Tactical voting
Encyclopedia
In voting system
s, tactical voting (or strategic voting or sophisticated voting) occurs, in elections with more than two viable candidates, when a voter supports a candidate other than his or her sincere preference in order to prevent an undesirable outcome.
It has been shown by the Gibbard-Satterthwaite theorem
that any voting method which is completely strategy-free must be either dictatorial or nondeterministic (that is, might not select the same outcome every time it is applied to the same set of voter preferences). For instance, the random ballot
voting method, which randomly selects the ballot of a single voter and uses this to determine the outcome, is strategy-free, but may result in different choices being selected if applied multiple times to the same set of ballots.
For example, in a simple plurality election
, a voter might sometimes gain a "better" outcome by voting for a less preferred but more generally popular candidate.
However, the type of tactical voting and the extent to which it affects the character of the campaign and the results of the election vary dramatically from one voting system to another.
candidate over an unpopular conservative candidate in order to help defeat a popular leftist candidate.) Duverger's law
suggests that, for this reason, first-past-the-post election systems will lead to two-party system
s in most cases. In those proportional representation
systems that include a minimum percentage of votes that a party must achieve to receive any seats, people might vote tactically for a minor party to prevent it from dropping below that percentage (which would make the votes it does receive useless for the larger political camp that party belongs to), or alternatively those who support the viewpoints of a minor party may vote for the larger party whose views are closest to those of the minor party.
or in a Condorcet method
, a voter may insincerely rank a perceived strong alternative last in order to help his or her preferred alternative beat it.
when a voter already believes that their favored candidate will make it to the next round – the voter then ranks an unpreferred, but easily beatable, candidate higher so that their preferred candidate can win later. In the United States
, for instance, voters of one party sometimes vote in the other party's primary
to nominate a candidate who will be easy for their favorite to beat, especially after that favorite has secured his party's own nomination.
is when a voter votes for just one candidate, despite having the option to vote for more than one due to a voting system such as approval voting
or plurality-at-large voting
. A voter helps his or her preferred candidate by not supplying votes to potential rivals. This strategy is encouraged and seen as sometimes beneficial in the systems of limited voting
and cumulative voting
.
. During the Republican primaries, Republicans
' Richard Riordan
(former mayor of Los Angeles
) and Bill Simon (a self-financed businessman) were vying for a chance to compete against the unpopular incumbent Democratic
Governor of California
, Gray Davis
. Polls predicted that Riordan would defeat Davis, while Simon would not.
At that time, the Republican primaries were open primaries
in which anyone could vote regardless of her or his own party affiliation, Davis supporters were rumored to have voted for Simon because Riordan was perceived as a greater threat to Davis; this combined with a negative advertising campaign by Davis describing Riordan as a "big-city liberal", and Simon ultimately won the primary despite a last-minute business scandal
. However, he lost the election against Davis; discontent soon led to the recall
.
In United Kingdom
elections, there are three main parties represented in the Parliament: the Labour party
, the Conservative party
and the Liberal Democrats. Of these three, Labour and the Liberal Democrats are considered similar by many voters. Many people who prefer the Liberal Democrats vote for the Labour candidate where Labour is stronger and vice-versa where the Liberal Democrats are stronger, in order to prevent the Conservative candidate from winning.
In the 1997 UK general election
, Democratic Left
helped Bruce Kent
set up GROT - Get Rid Of Them - a tactical voter campaign whose sole aim was to help prevent the Conservative Party from gaining a 5th term in office. This coalition was drawn from individuals in all the main opposition parties and many who were not aligned with any party. While it would be hard to prove that GROT swung the election itself, it did attract significant media attention and brought tactical voting into the mainstream for the first time in UK politics. In 2001, the Democratic Left's successor organisation the New Politics Network
organised a similar campaign tacticalvoter.net. Since then tactical voting has become a real consideration in British politics as is reflected in by-elections and by the growth in sites such as tacticalvoting.com who encourage tactical voting as a way of defusing the two party system and empowering the individual voter. In the 2005 UK General Election individuals set up tacticalvoting.net to balance the tactical voting debate.
In the Ontario general election, 1999
, strategic voting was widely encouraged by opponents of the Progressive Conservative government of Mike Harris
. This failed to unseat Harris, and succeeded only in suppressing the New Democratic Party vote to a historic low.
In the Canadian general election, 2004 and to a lesser extent in the Canadian general election, 2006, strategic voting was a concern for the federal New Democratic Party. In the 2004 election, the governing Liberal Party was able to convince many New Democratic voters to vote Liberal in order to avoid a Conservative government. In the 2006 elections, the Liberal Party attempted the same strategy, with Prime Minister Paul Martin
asking New Democrats and Greens to vote for the Liberal Party in order to prevent a Conservative win. The New Democratic Party leader Jack Layton
would respond by asking voters to "lend" their votes to his party, suggesting that the Liberal Party would be bound to lose the election regardless of strategic voting.
In the 2006 local elections in London, tactical voting is being promoted by sites such as London Strategic Voter in a response to national and international issues. The question of whether this approach acts to undermine local democracy is receiving much debate.
In Northern Ireland, it is widely believed that (predominantly Protestant) Unionist voters in Nationalist strongholds have voted for the Social Democratic and Labour Party
(SDLP) to prevent Sinn Féin
from capturing such seats. This conclusion was reached by comparing results to the demographics of constituencies and polling districts.
In Hong Kong, with its largest remainder method with the Hare quota
, voters supporting candidates of the pro-democracy camp
will organise to cast their votes to different tickets, so as to avoid votes being concentrated on one or a few candidates and wasted.
Puerto Rico
's 2004 elections were affected by tactical voting. The New Progressive Party
's candidate was unpopular, except among the pro-statehood Right, because of large corruption schemes and privatization of public corporations. To prevent him from winning, other factions supported the Partido Popular Democratico's candidate. The elections were close; statehood advocates won a seat in the U.S. house of representatives and majorities in both legislative branches, but lost governance to Anibal Acevedo Vila
. (In Puerto Rico you have the chance to vote by party or by candidate. Separatists voted under their ideology, but for the center party's candidate. This caused major turmoil.) After a recount and a trial, Anibal Acevedo Vila
was certified as governor of the commonwealth of Puerto Rico.
. In this model, voters are short-term instrumentally rational. That is, voters are only voting in order to make an impact on one election at a time (not, say, to build the political party for next election); voters have a set of sincere preferences, or utility rankings, by which to rate candidates; voters have some knowledge of each other's preferences; and voters understand how best to use tactical voting to their advantage. The extent to which this model resembles real-life elections is the subject of considerable academic debate.
and Weber. The strategy is broadly applicable to a number of single-winner voting systems that are additive point systems, such as Plurality
, Borda
, Approval
, and Range
. The strategy is optimal in the sense that the strategy will maximize the voter's expected utility when the number of voters is sufficiently large.
This rational voter model assumes that the voter's utility of the election result is dependent only on which candidate wins and not on any other aspect of the election, for example showing support for a losing candidate in the vote tallies. The model also assumes the voter chooses how to vote individually and not in collaboration with other voters.
Given a set of k candidates and a voter let:
Then the voter's prospective rating for a candidate i is defined as:
The gain in expected utility for a given vote is given by:
The gain in expected utility can be maximized by choosing a vote with suitable values of vi, depending on the voting system and the voter's prospective ratings for each candidate. For specific voting systems, the gain can be maximized using the following rules:
An important special case occurs when the voter has no information about how other voters will vote. This is sometimes referred to as the zero information strategy. In this special case, the pij pivot probabilities are all equal and the rules for the specific voting systems become:
Myerson and Weber also describe voting equilibria that require all voters use the optimal strategy and all voters share a common set of pij pivot probabilities. Because of these additional requirements, such equilibria may in practice be less widely applicable than the strategies.
In rolling election
s, or runoff votes
, where some voters have information about previous voters' preferences (e.g. presidential primaries
in the United States
, French
presidential elections), candidates put disproportionate resources into competing strongly in the first few stages, because those stages affect the reaction of later stages.
British Labour Party politician Anne Begg
warned of the dangers of tactical voting:
Tactical voting is commonly regarded as a problem, since it makes the actual ballot into a nontrivial game
, where voters react and counter-react to what they expect other voters' strategies to be. British mathematician Charles Dodgson (a.k.a. Lewis Carroll
) was, apparently, the first to acknowledge this fact. A game such as this might even result in a worse alternative being chosen, because most of the voters used it as a strategic tool. However the existence of limited tactical voting can be thought to increase the quality of the candidates elected because it takes into account not just the "ranking" of the candidates but also the utilities.
Though Arrow's impossibility theorem
and Gibbard-Satterthwaite theorem
prove that any useful voting system based on preference ranking is prone to some kind of manipulation, some use game theory
to search for some kind of "minimally manipulatable" (incentive compatibility
) voting schemes.
Game theory can also be used to analyze the pros and cons of different methods. For instance, under purely honest voting, Condorcet method
-like systems tend to settle on compromise candidates, while Instant-Runoff Voting
favors those candidates which have strong core support - who may often be more extremist. An electorate using one of these two systems but which (in the general or the specific case) preferred the characteristics of the other system could consciously use strategy to achieve a result more characteristic of the other system. Under Condorcet, they may be able to win by "burying" the compromise candidate (although this risks throwing the election to the opposing extreme); while under IRV, they could always "compromise". It could be argued that in this case the option to vote tactically or not actually helps the electorate express its will, not only on which candidate is better, but on whether compromise is desirable. (This never applies to "sneakier" tactics such as push-over.)
Tactical voting greatly complicates the comparative analysis of voting systems. If tactical voting were to become significant, the perceived "advantages" of a given voting system (that is, tending towards compromise or favoring core support) could turn into disadvantages - and, more surprisingly, vice versa.
Moreover, although by the Gibbard-Satterthwaite theorem no deterministic voting system is immune to tactical voting in all cases, some systems' results are more resistant to tactical voting than others'. M. Badinski and R. Laraki, the inventors of the majority judgment
system, performed an initial investigation of this question using a set of Monte Carlo
simulated elections based on the results from a poll of the 2007 French presidential election which they had carried out using rated ballots. Comparing range voting
, Borda count
, plurality voting, approval voting
with two different absolute approval thresholds, Condorcet voting, and majority judgment
, they found that range voting had the highest (worst) strategic vulnerability, while their own system majority judgment had the lowest (best). Further investigation would be needed to be sure that this result remained true with different sets of candidates.
elections. The most typical tactic is to assess which two candidates are frontrunners — that is, most likely to win — and to vote for the preferred one of those two, even if a third candidate is preferred over both. In fact, Duverger's law
states that this kind of tactical voting — along with the spoiler effect
which can arise when such tactics are not used — will be so common that any system based on plurality will eventually result in two-party domination. Although this "law" is just an empirical observation rather than a mathematical certainty, it is generally supported by the evidence.
Due to the especially deep impact of tactical voting in first past the post electoral systems, some argue that systems with three or more strong or persistent parties become in effect forms of disapproval voting
, where the expression of disapproval in order to keep an opponent out of office overwhelms the expression of approval to elect a desirable candidate. Ralph Nader
refers to this as the "least worst" choice, and argues that the similarity of parties and the candidates in first past the post systems grows stronger due to the need to avoid this disapproval.
, strategy is typically "semi-honest exaggeration"; that is, voters exaggerate the difference between a certain pair of candidates, but do not rank any less-preferred candidate over any more-preferred one. Even this form of exaggeration can only have an effect if the voter's honest rating for the intended winner is below that candidate's median rating or their honest rating for the intended loser is above it. Typically this would not be the case unless there were two similar candidates favored by the same set of voters. A strategic vote against a similar rival could result in a favored candidate winning; although if voters for both similar rivals used this strategy, it could cause a candidate favored by neither of these voter groups to win.
Balinski and Laraki argue that the fact that, under majority judgment, many voters have no opportunity to use strategy is why they found, in a test using simulated elections based on polling data, that this system was the most strategy-resistant of the ones they studied.
, unlike many other systems, strategy almost never involves ranking a less-preferred candidate over a more-preferred one. However, strategy is in fact inevitable when a voter decides their "approval cutoff"; this is a variation of the compromising strategy. Overall, Steven Brams
and Dudley R. Herschbach
argued in a paper in Science
magazine in 2001 that approval voting
was the system least amenable to tactical perturbations. Meanwhile, Balinski and Laraki used rated ballots from a poll of the 2007 French presidential election to show that, if unstrategic voters only approved candidates whom they considered "very good" or better, strategic voters would be able to sway the result frequently, but that if unstrategic voters approved all candidates they considered "good" or better, approval was the second most strategy-resistant system of the ones they studied.
One simple situation in which Approval strategy is important is if there is a close election between two similar candidates A and B and one distinct one Z, in which Z has 49% support. If all of Z's supporters approve just him, in hopes of him getting just enough to win, then supporters of A are faced with a tactical choice of whether to approve A and B (getting one of their preferred choices but having no say in which) or approving just A (possibly helping choose her over B, but risking throwing the election to Z). B's supporters face the same dilemma.
, strategic voters who expect all other voters to be strategic will exaggerate their true preferences and use the same quasi-compromising strategy as in approval voting, above. That is, they will give all candidates either the highest possible or the lowest possible ranking. This presents an additional problem as compared to the approval system if some voters give honest "weak" votes with middle rankings and other voters give strategic approval votes. A strategic minority could overpower an honest majority. To minimize this problem, some range voting advocates suggest measures such as education or ballot design to encourage uninformed voters to give more-extreme rankings. A different path to minimize this problem is to use median scores instead of total scores, as median scores are less amenable to exaggeration, as in majority judgment
.
However, if all voter factions have the same proportion of strategic and honest voters, simulations show that any significant proportion of honest voters will lead to results which tend to be more satisfying to voters than approval voting, and indeed, more satisfying any other system with the same unbiased proportion of strategic voters.
In a simulation study using polling data collected under a majority judgment system, that system's designers found that range voting was more vulnerable to strategy than any other system they studied, including plurality.
.
s have a further-reduced incentive for the compromising strategy, but they have some vulnerability to the burying strategy. The extent of this vulnerability depends on the particular Condorcet method. Some Condorcet methods arguably reduce the vulnerability to burying to the point where it is no longer a significant problem. All guaranteed Condorcet methods are vulnerable to the bullet voting strategy, because they violate the later-no-harm criterion
.
has both a strong compromising incentive and a large vulnerability to burying. Here is a hypothetical example of both factors at the same time: If there are two candidates whom a voter considers to be the most likely to win, the voter can maximize their impact on the contest between these candidates by ranking the candidate whom they like more in first place, and ranking the candidate whom they like less in last place. If neither candidate is their sincere first or last choice, the voter is employing both the compromising and burying strategies at once. If many different groups voters use this strategy, this gives a paradoxical advantage to the candidate who is generally thought least-likely to win.
has an incentive for free riding, a form of compromising strategy sometimes used in proportional representation systems. If one's top-choice candidate is elected, only a fraction of one's vote will be transferred to one's next-favoured candidate. If one feels the favoured candidate is certain to be elected in any case, insincerely ranking the second candidate first guarantees them a full vote if needed. However, the greater the certainty of the first candidate being elected, the bigger their likely surplus, the higher the fraction of the vote that would be transferred to the next candidate, and hence the lower the proportionate benefit of tactical voting.
More sophisticated tactics may be practicable where the number of candidates, voters and/or seats to be filled is relatively small.
Some forms of STV allow tactical voters to gain an advantage by listing a candidate who is very likely to lose in first place, as a form of pushover. Meek's method
essentially eliminates this strategy.
Voting system
A voting system or electoral system is a method by which voters make a choice between options, often in an election or on a policy referendum....
s, tactical voting (or strategic voting or sophisticated voting) occurs, in elections with more than two viable candidates, when a voter supports a candidate other than his or her sincere preference in order to prevent an undesirable outcome.
It has been shown by the Gibbard-Satterthwaite theorem
Gibbard-Satterthwaite theorem
The Gibbard–Satterthwaite theorem, named after Allan Gibbard and Mark Satterthwaite, is a result about the deterministic voting systems that choose a single winner using only the preferences of the voters, where each voter ranks all candidates in order of preference...
that any voting method which is completely strategy-free must be either dictatorial or nondeterministic (that is, might not select the same outcome every time it is applied to the same set of voter preferences). For instance, the random ballot
Random ballot
The random ballot is a hypothetical voting method; in an election or referendum, the ballot of a single voter is selected at random, and that ballot decides the result of the election...
voting method, which randomly selects the ballot of a single voter and uses this to determine the outcome, is strategy-free, but may result in different choices being selected if applied multiple times to the same set of ballots.
For example, in a simple plurality election
Plurality voting system
The plurality voting system is a single-winner voting system often used to elect executive officers or to elect members of a legislative assembly which is based on single-member constituencies...
, a voter might sometimes gain a "better" outcome by voting for a less preferred but more generally popular candidate.
However, the type of tactical voting and the extent to which it affects the character of the campaign and the results of the election vary dramatically from one voting system to another.
Compromising
Compromising (sometimes "useful vote") is a type of tactical voting in which a voter insincerely ranks an alternative higher in the hope of getting it elected. For example, in the first-past-the-post election, voters may vote for an option they perceive as having a greater chance of winning over an option they prefer (e.g., a conservative voter voting for a popular moderateModerate
In politics and religion, a moderate is an individual who is not extreme, partisan or radical. In recent years, political moderates has gained traction as a buzzword....
candidate over an unpopular conservative candidate in order to help defeat a popular leftist candidate.) Duverger's law
Duverger's law
In political science, Duverger's law is a principle which asserts that a plurality rule election system tends to favor a two-party system. This is one of two hypotheses proposed by Duverger, the second stating that “the double ballot majority system and proportional representation tend to...
suggests that, for this reason, first-past-the-post election systems will lead to two-party system
Two-party system
A two-party system is a system where two major political parties dominate voting in nearly all elections at every level of government and, as a result, all or nearly all elected offices are members of one of the two major parties...
s in most cases. In those proportional representation
Proportional representation
Proportional representation is a concept in voting systems used to elect an assembly or council. PR means that the number of seats won by a party or group of candidates is proportionate to the number of votes received. For example, under a PR voting system if 30% of voters support a particular...
systems that include a minimum percentage of votes that a party must achieve to receive any seats, people might vote tactically for a minor party to prevent it from dropping below that percentage (which would make the votes it does receive useless for the larger political camp that party belongs to), or alternatively those who support the viewpoints of a minor party may vote for the larger party whose views are closest to those of the minor party.
Burying
Burying is a type of tactical voting in which a voter insincerely ranks an alternative lower in the hopes of defeating it. For example, in the Borda countBorda count
The Borda count is a single-winner election method in which voters rank candidates in order of preference. The Borda count determines the winner of an election by giving each candidate a certain number of points corresponding to the position in which he or she is ranked by each voter. Once all...
or in a Condorcet method
Condorcet method
A Condorcet method is any single-winner election method that meets the Condorcet criterion, which means the method always selects the Condorcet winner if such a candidate exists. The Condorcet winner is the candidate who would beat each of the other candidates in a run-off election.In modern...
, a voter may insincerely rank a perceived strong alternative last in order to help his or her preferred alternative beat it.
Push-over
Push-over (also called mischief voting) is a type of tactical voting in which a voter ranks a perceived weak alternative higher, but not in the hopes of getting it elected. This primarily occurs in runoff votingTwo-round system
The two-round system is a voting system used to elect a single winner where the voter casts a single vote for their chosen candidate...
when a voter already believes that their favored candidate will make it to the next round – the voter then ranks an unpreferred, but easily beatable, candidate higher so that their preferred candidate can win later. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, for instance, voters of one party sometimes vote in the other party's primary
Party Raiding
Party Raiding is the term for members of one political party voting in another party's primary in an effort to either nominate a weaker candidate or at the very least prolong divided support between two or more contenders for that party's nomination .Party raiding can only occur in jurisdictions...
to nominate a candidate who will be easy for their favorite to beat, especially after that favorite has secured his party's own nomination.
Bullet voting
Bullet votingBullet voting
Bullet voting is a tactic in which the voter only selects one candidate, despite the option to indicate a preference for other candidates. They might do this either because it is easier than evaluating all the candidates, or as a form of tactical voting.If enough voters bullet vote, almost any...
is when a voter votes for just one candidate, despite having the option to vote for more than one due to a voting system such as approval voting
Approval voting
Approval voting is a single-winner voting system used for elections. Each voter may vote for as many of the candidates as the voter wishes. The winner is the candidate receiving the most votes. Each voter may vote for any combination of candidates and may give each candidate at most one vote.The...
or plurality-at-large voting
Plurality-at-large voting
Plurality-at-large voting is a non-proportional voting system for electing several representatives from a single multimember electoral district using a series of check boxes and tallying votes similar to a plurality election...
. A voter helps his or her preferred candidate by not supplying votes to potential rivals. This strategy is encouraged and seen as sometimes beneficial in the systems of limited voting
Limited Voting
Limited voting is a voting system in which electors have fewer votes than there are positions available. The positions are awarded to the candidates who receive the most votes absolutely...
and cumulative voting
Cumulative voting
Cumulative voting is a multiple-winner voting system intended to promote more proportional representation than winner-take-all elections.- History :...
.
Examples in real elections
One high-profile example of tactical voting was the California gubernatorial election, 2002California gubernatorial election, 2002
The 2002 California gubernatorial election was an election that occurred on November 5, 2002. Democrat Gray Davis defeated Republican Bill Simon by 5% and was re-elected to a second four-year term as Governor of California. Davis would be recalled less than a year into his next term.The 2002...
. During the Republican primaries, Republicans
Republican Party (United States)
The Republican Party is one of the two major contemporary political parties in the United States, along with the Democratic Party. Founded by anti-slavery expansion activists in 1854, it is often called the GOP . The party's platform generally reflects American conservatism in the U.S...
' Richard Riordan
Richard Riordan
Richard J. Riordan is a Republican politician from California, U.S.A. who served as the California Secretary for Education from 2003–2005 and as the 39th Mayor of Los Angeles, California from 1993–2001...
(former mayor of Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
) and Bill Simon (a self-financed businessman) were vying for a chance to compete against the unpopular incumbent Democratic
Democratic Party (United States)
The Democratic Party is one of two major contemporary political parties in the United States, along with the Republican Party. The party's socially liberal and progressive platform is largely considered center-left in the U.S. political spectrum. The party has the lengthiest record of continuous...
Governor of California
Governor of California
The Governor of California is the chief executive of the California state government, whose responsibilities include making annual State of the State addresses to the California State Legislature, submitting the budget, and ensuring that state laws are enforced...
, Gray Davis
Gray Davis
Joseph Graham "Gray" Davis, Jr. is an American Democratic politician who served as California's 37th Governor from 1999 until being recalled in 2003...
. Polls predicted that Riordan would defeat Davis, while Simon would not.
At that time, the Republican primaries were open primaries
Open primary
An open primary is a primary election that does not require voters to be affiliated with a political party in order to vote for partisan candidates. In a traditional open primary, voters may select one party's ballot and vote for that party's nomination. As in a closed primary, the highest voted...
in which anyone could vote regardless of her or his own party affiliation, Davis supporters were rumored to have voted for Simon because Riordan was perceived as a greater threat to Davis; this combined with a negative advertising campaign by Davis describing Riordan as a "big-city liberal", and Simon ultimately won the primary despite a last-minute business scandal
Scandal
A scandal is a widely publicized allegation or set of allegations that damages the reputation of an institution, individual or creed...
. However, he lost the election against Davis; discontent soon led to the recall
Recall election
A recall election is a procedure by which voters can remove an elected official from office through a direct vote before his or her term has ended...
.
In United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
elections, there are three main parties represented in the Parliament: the Labour party
Labour Party (UK)
The Labour Party is a centre-left democratic socialist party in the United Kingdom. It surpassed the Liberal Party in general elections during the early 1920s, forming minority governments under Ramsay MacDonald in 1924 and 1929-1931. The party was in a wartime coalition from 1940 to 1945, after...
, the Conservative party
Conservative Party (UK)
The Conservative Party, formally the Conservative and Unionist Party, is a centre-right political party in the United Kingdom that adheres to the philosophies of conservatism and British unionism. It is the largest political party in the UK, and is currently the largest single party in the House...
and the Liberal Democrats. Of these three, Labour and the Liberal Democrats are considered similar by many voters. Many people who prefer the Liberal Democrats vote for the Labour candidate where Labour is stronger and vice-versa where the Liberal Democrats are stronger, in order to prevent the Conservative candidate from winning.
In the 1997 UK general election
United Kingdom general election, 1997
The United Kingdom general election, 1997 was held on 1 May 1997, more than five years after the previous election on 9 April 1992, to elect 659 members to the British House of Commons. The Labour Party ended its 18 years in opposition under the leadership of Tony Blair, and won the general...
, Democratic Left
Democratic Left (United Kingdom)
Democratic Left was a post-communist political organisation in the United Kingdom during the 1990s, growing out of the Eurocommunist strand within the Communist Party of Great Britain and its magazine Marxism Today...
helped Bruce Kent
Bruce Kent
Bruce Kent is a British political activist and a former Roman Catholic priest. Active in the Campaign for Nuclear Disarmament , he was the organisation's general secretary from 1980 to 1985 and its chair from 1987 to 1990...
set up GROT - Get Rid Of Them - a tactical voter campaign whose sole aim was to help prevent the Conservative Party from gaining a 5th term in office. This coalition was drawn from individuals in all the main opposition parties and many who were not aligned with any party. While it would be hard to prove that GROT swung the election itself, it did attract significant media attention and brought tactical voting into the mainstream for the first time in UK politics. In 2001, the Democratic Left's successor organisation the New Politics Network
New Politics Network
The New Politics Network was an independent political and campaigning think tank in the United Kingdom, concerned with democratic renewal and popular participation in politics...
organised a similar campaign tacticalvoter.net. Since then tactical voting has become a real consideration in British politics as is reflected in by-elections and by the growth in sites such as tacticalvoting.com who encourage tactical voting as a way of defusing the two party system and empowering the individual voter. In the 2005 UK General Election individuals set up tacticalvoting.net to balance the tactical voting debate.
In the Ontario general election, 1999
Ontario general election, 1999
An Ontario general election was held on June 3, 1999, to elect members of the 37th Legislative Assembly of the Province of Ontario, Canada....
, strategic voting was widely encouraged by opponents of the Progressive Conservative government of Mike Harris
Mike Harris
Michael Deane "Mike" Harris was the 22nd Premier of Ontario from June 26, 1995 to April 15, 2002. He is most noted for the "Common Sense Revolution", his Progressive Conservative government's program of deficit reduction in combination with lower taxes and cuts to government...
. This failed to unseat Harris, and succeeded only in suppressing the New Democratic Party vote to a historic low.
In the Canadian general election, 2004 and to a lesser extent in the Canadian general election, 2006, strategic voting was a concern for the federal New Democratic Party. In the 2004 election, the governing Liberal Party was able to convince many New Democratic voters to vote Liberal in order to avoid a Conservative government. In the 2006 elections, the Liberal Party attempted the same strategy, with Prime Minister Paul Martin
Paul Martin
Paul Edgar Philippe Martin, PC , also known as Paul Martin, Jr. is a Canadian politician who was the 21st Prime Minister of Canada, as well as leader of the Liberal Party of Canada....
asking New Democrats and Greens to vote for the Liberal Party in order to prevent a Conservative win. The New Democratic Party leader Jack Layton
Jack Layton
John Gilbert "Jack" Layton, PC was a Canadian social democratic politician and the Leader of the Official Opposition. He was the leader of the New Democratic Party from 2003 to 2011, and previously sat on Toronto City Council, serving at times during that period as acting mayor and deputy mayor of...
would respond by asking voters to "lend" their votes to his party, suggesting that the Liberal Party would be bound to lose the election regardless of strategic voting.
In the 2006 local elections in London, tactical voting is being promoted by sites such as London Strategic Voter in a response to national and international issues. The question of whether this approach acts to undermine local democracy is receiving much debate.
In Northern Ireland, it is widely believed that (predominantly Protestant) Unionist voters in Nationalist strongholds have voted for the Social Democratic and Labour Party
Social Democratic and Labour Party
The Social Democratic and Labour Party is a social-democratic, Irish nationalist political party in Northern Ireland. Its basic party platform advocates Irish reunification, and the further devolution of powers while Northern Ireland remains part of the United Kingdom...
(SDLP) to prevent Sinn Féin
Sinn Féin
Sinn Féin is a left wing, Irish republican political party in Ireland. The name is Irish for "ourselves" or "we ourselves", although it is frequently mistranslated as "ourselves alone". Originating in the Sinn Féin organisation founded in 1905 by Arthur Griffith, it took its current form in 1970...
from capturing such seats. This conclusion was reached by comparing results to the demographics of constituencies and polling districts.
In Hong Kong, with its largest remainder method with the Hare quota
Hare quota
The Hare quota is a formula used under some forms of the Single Transferable Vote system and the largest remainder method of party-list proportional representation...
, voters supporting candidates of the pro-democracy camp
Pro-democracy camp
Pro-democracy camp, pan-democracy camp or pan-democrats refer to the politicians and social activists in Hong Kong who support increased democracy and may work together in areas of common interest or by not fielding candidates against one another in elections.Democratic activists are usually...
will organise to cast their votes to different tickets, so as to avoid votes being concentrated on one or a few candidates and wasted.
Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
's 2004 elections were affected by tactical voting. The New Progressive Party
New Progressive Party
The New Progressive Party is a name used by various political parties:* New Progressive Party of Puerto Rico* New Progressive Party -See also:*Progressive Party *List of political parties by name...
's candidate was unpopular, except among the pro-statehood Right, because of large corruption schemes and privatization of public corporations. To prevent him from winning, other factions supported the Partido Popular Democratico's candidate. The elections were close; statehood advocates won a seat in the U.S. house of representatives and majorities in both legislative branches, but lost governance to Anibal Acevedo Vila
Aníbal Acevedo Vilá
Aníbal Salvador Acevedo Vilá is a Puerto Rican politician and lawyer. He served as the eighth Governor of the Commonwealth of Puerto Rico, a Commonwealth of the United States, from 2005 to 2009. He is a Harvard University alumnus and a graduate of the University of Puerto Rico School of Law,...
. (In Puerto Rico you have the chance to vote by party or by candidate. Separatists voted under their ideology, but for the center party's candidate. This caused major turmoil.) After a recount and a trial, Anibal Acevedo Vila
Aníbal Acevedo Vilá
Aníbal Salvador Acevedo Vilá is a Puerto Rican politician and lawyer. He served as the eighth Governor of the Commonwealth of Puerto Rico, a Commonwealth of the United States, from 2005 to 2009. He is a Harvard University alumnus and a graduate of the University of Puerto Rico School of Law,...
was certified as governor of the commonwealth of Puerto Rico.
Rational voter model
Academic analysis of tactical voting is based on the rational voter model, derived from rational choice theoryRational choice theory
Rational choice theory, also known as choice theory or rational action theory, is a framework for understanding and often formally modeling social and economic behavior. It is the main theoretical paradigm in the currently-dominant school of microeconomics...
. In this model, voters are short-term instrumentally rational. That is, voters are only voting in order to make an impact on one election at a time (not, say, to build the political party for next election); voters have a set of sincere preferences, or utility rankings, by which to rate candidates; voters have some knowledge of each other's preferences; and voters understand how best to use tactical voting to their advantage. The extent to which this model resembles real-life elections is the subject of considerable academic debate.
Myerson-Weber strategy
An example of a rational voter strategy is described by MyersonRoger Myerson
Roger Bruce Myerson is an American economist and Nobel laureate recognized with Leonid Hurwicz and Eric Maskin for "having laid the foundations of mechanism design theory." A professor at the University of Chicago, he has made contributions as an economist, as an applied mathematician, and as a...
and Weber. The strategy is broadly applicable to a number of single-winner voting systems that are additive point systems, such as Plurality
Plurality voting system
The plurality voting system is a single-winner voting system often used to elect executive officers or to elect members of a legislative assembly which is based on single-member constituencies...
, Borda
Borda count
The Borda count is a single-winner election method in which voters rank candidates in order of preference. The Borda count determines the winner of an election by giving each candidate a certain number of points corresponding to the position in which he or she is ranked by each voter. Once all...
, Approval
Approval voting
Approval voting is a single-winner voting system used for elections. Each voter may vote for as many of the candidates as the voter wishes. The winner is the candidate receiving the most votes. Each voter may vote for any combination of candidates and may give each candidate at most one vote.The...
, and Range
Range voting
Range voting is a voting system for one-seat elections under which voters score each candidate, the scores are added up, and the candidate with the highest score wins.A form of range voting was apparently used in...
. The strategy is optimal in the sense that the strategy will maximize the voter's expected utility when the number of voters is sufficiently large.
This rational voter model assumes that the voter's utility of the election result is dependent only on which candidate wins and not on any other aspect of the election, for example showing support for a losing candidate in the vote tallies. The model also assumes the voter chooses how to vote individually and not in collaboration with other voters.
Given a set of k candidates and a voter let:
- vi = the number of points to be voted for candidate i
- ui = the voter's gain in utility if candidate i wins the election
- pij = the (voter's perceived) pivot probability that candidates i and j will be tied for the most total points to win the election.
Then the voter's prospective rating for a candidate i is defined as:
The gain in expected utility for a given vote is given by:
The gain in expected utility can be maximized by choosing a vote with suitable values of vi, depending on the voting system and the voter's prospective ratings for each candidate. For specific voting systems, the gain can be maximized using the following rules:
- Plurality: Vote for the candidate with the highest prospective rating. This is to be distinguished from choosing the best of the frontrunners, which is a common but imprecise plurality tactic. The highest prospective rating can in fact belong to a weak candidate, even the weakest.
- Borda: Rank the candidates in decreasing order of prospective rating.
- Approval: Vote for all candidates that have a positive prospective rating; do not vote for any candidates that have a negative prospective rating.
- Range: Vote the maximum points for all candidates that have a positive prospective rating; vote the minimum allowed value for all candidates that have a negative prospective rating; vote any number of points for a candidate with a prospective rating of zero.
An important special case occurs when the voter has no information about how other voters will vote. This is sometimes referred to as the zero information strategy. In this special case, the pij pivot probabilities are all equal and the rules for the specific voting systems become:
- Plurality: Vote for the most preferred (highest utility) candidate. This is the sincere plurality vote.
- Borda: Rank the candidates in decreasing order preference (decreasing order of utility). This is the sincere ranking of the candidates.
- Approval: Calculate the average utility of all candidates. Vote for all candidates that have a higher-than-average utility; do not vote for any candidates that have a lower-than-average utility.
- Range: Calculate the average utility of all candidates. Vote the maximum points for all candidates that have a higher-than-average utility; vote the minimum points for all candidates that have a lower-than-average utility; vote any value for a candidate with a utility equal to the average.
Myerson and Weber also describe voting equilibria that require all voters use the optimal strategy and all voters share a common set of pij pivot probabilities. Because of these additional requirements, such equilibria may in practice be less widely applicable than the strategies.
Pre-election influence
Because tactical voting relies heavily on voters' perception of how other voters intend to vote, campaigns in electoral systems that promote compromise frequently focus on affecting voter's perception of campaign viability. Most campaigns craft refined media strategies to shape the way voters see their candidacy. During this phase, there can be an analogous effect where campaign donors and activists may decide whether or not to support candidates tactically with their money and labor.In rolling election
Rolling election
Rolling elections are elections in which all representatives in a body are reelected, but these elections are spread over a period of time rather than all at once. Examples are the presidential primaries in the United States, and, due to logistics, general elections in Lebanon and India...
s, or runoff votes
Two-round system
The two-round system is a voting system used to elect a single winner where the voter casts a single vote for their chosen candidate...
, where some voters have information about previous voters' preferences (e.g. presidential primaries
Primary election
A primary election is an election in which party members or voters select candidates for a subsequent election. Primary elections are one means by which a political party nominates candidates for the next general election....
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
presidential elections), candidates put disproportionate resources into competing strongly in the first few stages, because those stages affect the reaction of later stages.
Views on tactical voting
Some people view tactical voting as providing misleading information. In this view, a ballot paper is asking the question "which of these candidates is the best?". This means that if one votes for a candidate who one does not believe is the best, then one is lying.British Labour Party politician Anne Begg
Anne Begg
Dame Anne Begg, DBE is a British Labour Party politician, who has been the Member of Parliament for Aberdeen South since 1997...
warned of the dangers of tactical voting:
- "Tactical voting is fine in theory and as an intellectual discussion in the drawing room or living rooms around the country, but when you actually get to polling day and you have to vote against your principles, then it is much harder to do." http://news.bbc.co.uk/1/hi/uk_politics/1091208.stm
Tactical voting is commonly regarded as a problem, since it makes the actual ballot into a nontrivial game
Game theory
Game theory is a mathematical method for analyzing calculated circumstances, such as in games, where a person’s success is based upon the choices of others...
, where voters react and counter-react to what they expect other voters' strategies to be. British mathematician Charles Dodgson (a.k.a. Lewis Carroll
Lewis Carroll
Charles Lutwidge Dodgson , better known by the pseudonym Lewis Carroll , was an English author, mathematician, logician, Anglican deacon and photographer. His most famous writings are Alice's Adventures in Wonderland and its sequel Through the Looking-Glass, as well as the poems "The Hunting of the...
) was, apparently, the first to acknowledge this fact. A game such as this might even result in a worse alternative being chosen, because most of the voters used it as a strategic tool. However the existence of limited tactical voting can be thought to increase the quality of the candidates elected because it takes into account not just the "ranking" of the candidates but also the utilities.
Though Arrow's impossibility theorem
Arrow's impossibility theorem
In social choice theory, Arrow’s impossibility theorem, the General Possibility Theorem, or Arrow’s paradox, states that, when voters have three or more distinct alternatives , no voting system can convert the ranked preferences of individuals into a community-wide ranking while also meeting a...
and Gibbard-Satterthwaite theorem
Gibbard-Satterthwaite theorem
The Gibbard–Satterthwaite theorem, named after Allan Gibbard and Mark Satterthwaite, is a result about the deterministic voting systems that choose a single winner using only the preferences of the voters, where each voter ranks all candidates in order of preference...
prove that any useful voting system based on preference ranking is prone to some kind of manipulation, some use game theory
Game theory
Game theory is a mathematical method for analyzing calculated circumstances, such as in games, where a person’s success is based upon the choices of others...
to search for some kind of "minimally manipulatable" (incentive compatibility
Incentive compatibility
In mechanism design, a process is said to be incentive-compatible if all of the participants fare best when they truthfully reveal any private information asked for by the mechanism. As an illustration, voting systems which create incentives to vote dishonestly lack the property of incentive...
) voting schemes.
Game theory can also be used to analyze the pros and cons of different methods. For instance, under purely honest voting, Condorcet method
Condorcet method
A Condorcet method is any single-winner election method that meets the Condorcet criterion, which means the method always selects the Condorcet winner if such a candidate exists. The Condorcet winner is the candidate who would beat each of the other candidates in a run-off election.In modern...
-like systems tend to settle on compromise candidates, while Instant-Runoff Voting
Instant-runoff voting
Instant-runoff voting , also known as preferential voting, the alternative vote and ranked choice voting, is a voting system used to elect one winner. Voters rank candidates in order of preference, and their ballots are counted as one vote for their first choice candidate. If a candidate secures a...
favors those candidates which have strong core support - who may often be more extremist. An electorate using one of these two systems but which (in the general or the specific case) preferred the characteristics of the other system could consciously use strategy to achieve a result more characteristic of the other system. Under Condorcet, they may be able to win by "burying" the compromise candidate (although this risks throwing the election to the opposing extreme); while under IRV, they could always "compromise". It could be argued that in this case the option to vote tactically or not actually helps the electorate express its will, not only on which candidate is better, but on whether compromise is desirable. (This never applies to "sneakier" tactics such as push-over.)
Tactical voting greatly complicates the comparative analysis of voting systems. If tactical voting were to become significant, the perceived "advantages" of a given voting system (that is, tending towards compromise or favoring core support) could turn into disadvantages - and, more surprisingly, vice versa.
Influence of voting system on tactical voting
Tactical voting is highly dependent on the voting system being used. A tactical vote which improves a voter's satisfaction under one system could make no change or lead to a less-satisfying result under another system.Moreover, although by the Gibbard-Satterthwaite theorem no deterministic voting system is immune to tactical voting in all cases, some systems' results are more resistant to tactical voting than others'. M. Badinski and R. Laraki, the inventors of the majority judgment
Majority Judgment
Majority Judgment is a single-winner voting system proposed by Michel Balinski and Rida Laraki. Voters freely grade each candidate in one of several named ranks, for instance from "excellent" to "bad", and the candidate with the highest median grade is the winner. If more than one candidate has the...
system, performed an initial investigation of this question using a set of Monte Carlo
Monte Carlo method
Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used in computer simulations of physical and mathematical systems...
simulated elections based on the results from a poll of the 2007 French presidential election which they had carried out using rated ballots. Comparing range voting
Range voting
Range voting is a voting system for one-seat elections under which voters score each candidate, the scores are added up, and the candidate with the highest score wins.A form of range voting was apparently used in...
, Borda count
Borda count
The Borda count is a single-winner election method in which voters rank candidates in order of preference. The Borda count determines the winner of an election by giving each candidate a certain number of points corresponding to the position in which he or she is ranked by each voter. Once all...
, plurality voting, approval voting
Approval voting
Approval voting is a single-winner voting system used for elections. Each voter may vote for as many of the candidates as the voter wishes. The winner is the candidate receiving the most votes. Each voter may vote for any combination of candidates and may give each candidate at most one vote.The...
with two different absolute approval thresholds, Condorcet voting, and majority judgment
Majority Judgment
Majority Judgment is a single-winner voting system proposed by Michel Balinski and Rida Laraki. Voters freely grade each candidate in one of several named ranks, for instance from "excellent" to "bad", and the candidate with the highest median grade is the winner. If more than one candidate has the...
, they found that range voting had the highest (worst) strategic vulnerability, while their own system majority judgment had the lowest (best). Further investigation would be needed to be sure that this result remained true with different sets of candidates.
First past the post / plurality voting
Tactical voting by compromising is exceedingly common in pluralityPlurality voting system
The plurality voting system is a single-winner voting system often used to elect executive officers or to elect members of a legislative assembly which is based on single-member constituencies...
elections. The most typical tactic is to assess which two candidates are frontrunners — that is, most likely to win — and to vote for the preferred one of those two, even if a third candidate is preferred over both. In fact, Duverger's law
Duverger's law
In political science, Duverger's law is a principle which asserts that a plurality rule election system tends to favor a two-party system. This is one of two hypotheses proposed by Duverger, the second stating that “the double ballot majority system and proportional representation tend to...
states that this kind of tactical voting — along with the spoiler effect
Spoiler effect
The spoiler effect describes the effect a minor party candidate with little chance of winning has in a close election, when that candidate's presence in the election draws votes from a major candidate similar to them, thereby causing a candidate dissimilar to them to win the election...
which can arise when such tactics are not used — will be so common that any system based on plurality will eventually result in two-party domination. Although this "law" is just an empirical observation rather than a mathematical certainty, it is generally supported by the evidence.
Due to the especially deep impact of tactical voting in first past the post electoral systems, some argue that systems with three or more strong or persistent parties become in effect forms of disapproval voting
Disapproval voting
Disapproval voting is any voting system that allows many voters to express formal disapproval simultaneously, in a system where they all share some power. Unlike most voting systems, it requires that only negative measures or choices be presented to the voter or representative...
, where the expression of disapproval in order to keep an opponent out of office overwhelms the expression of approval to elect a desirable candidate. Ralph Nader
Ralph Nader
Ralph Nader is an American political activist, as well as an author, lecturer, and attorney. Areas of particular concern to Nader include consumer protection, humanitarianism, environmentalism, and democratic government....
refers to this as the "least worst" choice, and argues that the similarity of parties and the candidates in first past the post systems grows stronger due to the need to avoid this disapproval.
Majority Judgment
In majority judgmentMajority Judgment
Majority Judgment is a single-winner voting system proposed by Michel Balinski and Rida Laraki. Voters freely grade each candidate in one of several named ranks, for instance from "excellent" to "bad", and the candidate with the highest median grade is the winner. If more than one candidate has the...
, strategy is typically "semi-honest exaggeration"; that is, voters exaggerate the difference between a certain pair of candidates, but do not rank any less-preferred candidate over any more-preferred one. Even this form of exaggeration can only have an effect if the voter's honest rating for the intended winner is below that candidate's median rating or their honest rating for the intended loser is above it. Typically this would not be the case unless there were two similar candidates favored by the same set of voters. A strategic vote against a similar rival could result in a favored candidate winning; although if voters for both similar rivals used this strategy, it could cause a candidate favored by neither of these voter groups to win.
Balinski and Laraki argue that the fact that, under majority judgment, many voters have no opportunity to use strategy is why they found, in a test using simulated elections based on polling data, that this system was the most strategy-resistant of the ones they studied.
Approval voting
Similarly, in approval votingApproval voting
Approval voting is a single-winner voting system used for elections. Each voter may vote for as many of the candidates as the voter wishes. The winner is the candidate receiving the most votes. Each voter may vote for any combination of candidates and may give each candidate at most one vote.The...
, unlike many other systems, strategy almost never involves ranking a less-preferred candidate over a more-preferred one. However, strategy is in fact inevitable when a voter decides their "approval cutoff"; this is a variation of the compromising strategy. Overall, Steven Brams
Steven Brams
Steven J. Brams is a game theorist and political scientist at the New York University Department of Politics. Brams is best known for using the techniques of game theory and public choice to research voting systems and fair division. He is one of the independent discoverers of approval voting...
and Dudley R. Herschbach
Dudley R. Herschbach
Dudley Robert Herschbach is an American chemist at Harvard University. He won the 1986 Nobel Prize in Chemistry jointly with Yuan T. Lee and John C...
argued in a paper in Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
magazine in 2001 that approval voting
Approval voting
Approval voting is a single-winner voting system used for elections. Each voter may vote for as many of the candidates as the voter wishes. The winner is the candidate receiving the most votes. Each voter may vote for any combination of candidates and may give each candidate at most one vote.The...
was the system least amenable to tactical perturbations. Meanwhile, Balinski and Laraki used rated ballots from a poll of the 2007 French presidential election to show that, if unstrategic voters only approved candidates whom they considered "very good" or better, strategic voters would be able to sway the result frequently, but that if unstrategic voters approved all candidates they considered "good" or better, approval was the second most strategy-resistant system of the ones they studied.
One simple situation in which Approval strategy is important is if there is a close election between two similar candidates A and B and one distinct one Z, in which Z has 49% support. If all of Z's supporters approve just him, in hopes of him getting just enough to win, then supporters of A are faced with a tactical choice of whether to approve A and B (getting one of their preferred choices but having no say in which) or approving just A (possibly helping choose her over B, but risking throwing the election to Z). B's supporters face the same dilemma.
Range voting
In range votingRange voting
Range voting is a voting system for one-seat elections under which voters score each candidate, the scores are added up, and the candidate with the highest score wins.A form of range voting was apparently used in...
, strategic voters who expect all other voters to be strategic will exaggerate their true preferences and use the same quasi-compromising strategy as in approval voting, above. That is, they will give all candidates either the highest possible or the lowest possible ranking. This presents an additional problem as compared to the approval system if some voters give honest "weak" votes with middle rankings and other voters give strategic approval votes. A strategic minority could overpower an honest majority. To minimize this problem, some range voting advocates suggest measures such as education or ballot design to encourage uninformed voters to give more-extreme rankings. A different path to minimize this problem is to use median scores instead of total scores, as median scores are less amenable to exaggeration, as in majority judgment
Majority Judgment
Majority Judgment is a single-winner voting system proposed by Michel Balinski and Rida Laraki. Voters freely grade each candidate in one of several named ranks, for instance from "excellent" to "bad", and the candidate with the highest median grade is the winner. If more than one candidate has the...
.
However, if all voter factions have the same proportion of strategic and honest voters, simulations show that any significant proportion of honest voters will lead to results which tend to be more satisfying to voters than approval voting, and indeed, more satisfying any other system with the same unbiased proportion of strategic voters.
In a simulation study using polling data collected under a majority judgment system, that system's designers found that range voting was more vulnerable to strategy than any other system they studied, including plurality.
Instant runoff voting
Instant runoff voting has a less incentive for the compromising strategy than plurality, plus a minor vulnerability to the push-over strategy. A burying strategy is entirely ineffective in IRV. The bullet voting strategy is also entirely ineffective in IRV, because IRV satisfies the later-no-harm criterionLater-no-harm criterion
The later-no-harm criterion is a voting system criterion formulated by Douglas Woodall. The criterion is satisfied if, in any election, a voter giving an additional ranking or positive rating to a less preferred candidate cannot cause a more preferred candidate to lose.- Complying methods :Single...
.
Condorcet
Condorcet methodCondorcet method
A Condorcet method is any single-winner election method that meets the Condorcet criterion, which means the method always selects the Condorcet winner if such a candidate exists. The Condorcet winner is the candidate who would beat each of the other candidates in a run-off election.In modern...
s have a further-reduced incentive for the compromising strategy, but they have some vulnerability to the burying strategy. The extent of this vulnerability depends on the particular Condorcet method. Some Condorcet methods arguably reduce the vulnerability to burying to the point where it is no longer a significant problem. All guaranteed Condorcet methods are vulnerable to the bullet voting strategy, because they violate the later-no-harm criterion
Later-no-harm criterion
The later-no-harm criterion is a voting system criterion formulated by Douglas Woodall. The criterion is satisfied if, in any election, a voter giving an additional ranking or positive rating to a less preferred candidate cannot cause a more preferred candidate to lose.- Complying methods :Single...
.
Borda
The Borda countBorda count
The Borda count is a single-winner election method in which voters rank candidates in order of preference. The Borda count determines the winner of an election by giving each candidate a certain number of points corresponding to the position in which he or she is ranked by each voter. Once all...
has both a strong compromising incentive and a large vulnerability to burying. Here is a hypothetical example of both factors at the same time: If there are two candidates whom a voter considers to be the most likely to win, the voter can maximize their impact on the contest between these candidates by ranking the candidate whom they like more in first place, and ranking the candidate whom they like less in last place. If neither candidate is their sincere first or last choice, the voter is employing both the compromising and burying strategies at once. If many different groups voters use this strategy, this gives a paradoxical advantage to the candidate who is generally thought least-likely to win.
Single Transferable Vote
The Single Transferable VoteSingle transferable vote
The single transferable vote is a voting system designed to achieve proportional representation through preferential voting. Under STV, an elector's vote is initially allocated to his or her most preferred candidate, and then, after candidates have been either elected or eliminated, any surplus or...
has an incentive for free riding, a form of compromising strategy sometimes used in proportional representation systems. If one's top-choice candidate is elected, only a fraction of one's vote will be transferred to one's next-favoured candidate. If one feels the favoured candidate is certain to be elected in any case, insincerely ranking the second candidate first guarantees them a full vote if needed. However, the greater the certainty of the first candidate being elected, the bigger their likely surplus, the higher the fraction of the vote that would be transferred to the next candidate, and hence the lower the proportionate benefit of tactical voting.
More sophisticated tactics may be practicable where the number of candidates, voters and/or seats to be filled is relatively small.
Some forms of STV allow tactical voters to gain an advantage by listing a candidate who is very likely to lose in first place, as a form of pushover. Meek's method
Counting Single Transferable Votes
The single transferable vote is a voting system based on proportional representation and preferential voting. Under STV, an elector's vote is initially allocated to his or her most-preferred candidate...
essentially eliminates this strategy.
Tactical unwind
The term "tactical unwind" is used by some political scientists and commentators to refer to the phenomenon when tactical voting takes place in one general election but in subsequent elections voters revert to their normal patterns.See also
- primary electionPrimary electionA primary election is an election in which party members or voters select candidates for a subsequent election. Primary elections are one means by which a political party nominates candidates for the next general election....
- political partyPolitical partyA political party is a political organization that typically seeks to influence government policy, usually by nominating their own candidates and trying to seat them in political office. Parties participate in electoral campaigns, educational outreach or protest actions...
- strategic nominationStrategic nominationStrategic nomination is the manipulation of an election through its candidate set...
- vote swapping
- electoral fusionElectoral fusionElectoral fusion is an arrangement where two or more political parties on a ballot list the same candidate, pooling the votes for that candidate...
- Unite the RightUnite the RightThe Unite the Right movement was a Canadian political movement which existed from around 1996 to 2003. The movement came into being when it became clear that neither of Canada's two main right-of-center political parties: the Reform Party of Canada or the Progressive Conservative Party of Canada...
- Tactical manipulation of runoff votingTactical manipulation of runoff votingLike virtually all electoral systems, in runoff voting there is potential for both tactical voting and strategic nomination. Tactical voting is where voters do not vote in accordance with their true preferences, but instead vote insincerely in an attempt to influence the result...
- Vote allocationVote allocationVote allocation is a system of tactical voting used in the Republic of China on Taiwan from the late-1990s until 2004, after which the voting system is to be changed from single non-transferable vote to a parallel voting system. In this system, voters are asked to vote for a party candidate based...
Resources
- Svensson, Lars-Gunnar (1999). The Proof of the Gibbard-Satterthwaite Theorem Revisited
- Brams, Herschbach (2001). "The Science of Elections, Science Online. Abstract
- Fisher, Stephen (2001). Extending the Rational Voter Theory of Tactical Voting
External links
- Tactical Voting Can Be a Weak Strategy -- Article on tactical voting within larger strategic considerations [archived]
- VotePair.org VotePair is a banding together of the people who started tactical voting online in the 2000 US elections.
- Results of 2005 UK election and suggesting tactical voting options for Sep. 2010