A single-member district or single-member constituency is an electoral district

Electoral district

An electoral district is a distinct territorial subdivision for holding a separate election for one or more seats in a legislative body...

 that returns one officeholder to a body with multiple members such as a legislature

Legislature

A legislature is a kind of deliberative assembly with the power to pass, amend, and repeal laws. The law created by a legislature is called legislation or statutory law. In addition to enacting laws, legislatures usually have exclusive authority to raise or lower taxes and adopt the budget and...

. This is also sometimes called single-winner voting.

Elections for single-member districts are held under a number of voting systems, including 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...

 (first past the post), runoffs

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...

, 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...

 (IRV), 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...

, 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...

, and 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...

s (such as the Minimax Condorcet

Minimax Condorcet

In voting systems, the Minimax method is one of several Condorcet methods used for tabulating votes and determining a winner when using preferential voting in a single-winner election...

, Schulze method

Schulze method

The Schulze method is a voting system developed in 1997 by Markus Schulze that selects a single winner using votes that express preferences. The method can also be used to create a sorted list of winners...

, and Ranked Pairs

Ranked Pairs

Ranked pairs or the Tideman method is a voting system developed in 1987 by Nicolaus Tideman that selects a single winner using votes that express preferences. RP can also be used to create a sorted list of winners....

). Of these, plurality and runoff voting are the most common.

Constituency link

A small constituency with a single member, as opposed to a large, multiple-member one, encourages a stronger connection between representative and constituent and increases accountability. In multi-member district countries such as Israel, where the whole country is treated as a single constituency and representatives are selected by party-lists, the constituency link is lost altogether.

It is often claimed that because each electoral district votes for its own representative, the elected candidate is held accountable to their own voters, thereby helping to prevent incompetent, fraudulent or corrupt behavior by elected candidates. The voters in the electoral district can easily replace him since they have full power over who they want to represent them.

On the other hand, in a constituency system, a candidate who is popular nationally may be removed if he is unpopular in his own district. This feature however is also present in open-list proportional systems.

Each representative must be a winner

Sometimes voters are in favour of a political party but do not like specific candidates. For example, voters in Canada re-elected the Alberta

Alberta

Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...

 government in 1989 but, because of dissatisfaction with its leadership, the premier and leader of the governing party, Don Getty

Don Getty

Donald Ross Getty, OC, AOE is a retired Canadian politician who served as the 11th Premier of Alberta between 1985 and 1992. A member of the Progressive Conservatives, he served as Energy Minister and Federal and Intergovernmental Affairs Minister in the government of Peter Lougheed before...

, lost his seat.

Fewer minority parties

Single-member districts tend to promote 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 (with some regional parties). Supporters view this as beneficial, as parliamentary governments are typically more stable in two-party systems, and thus small minorities are not given undue power to break a coalition. First-past-the-post minimizes the influence of third parties and thus arguably keeps out extremists.

Safe seats

A safe seat

Safe seat

A safe seat is a seat in a legislative body which is regarded as fully secured, either by a certain political party, the incumbent representative personally or a combination of both...

 is one in which a plurality or majority of voters, depending on the voting system, support a particular candidate or party so strongly that the candidate's election is practically guaranteed in advance of the vote. This means all other voters in the constituency make no difference to the result. This results in feelings of disenfranchisement and to abstention

Abstention

Abstention is a term in election procedure for when a participant in a vote either does not go to vote or, in parliamentary procedure, is present during the vote, but does not cast a ballot. Abstention must be contrasted with "blank vote", in which a voter casts a ballot willfully made invalid by...

ism among voters.

Comparison of single-member district election methods

	Monotonic Monotonicity criterion The monotonicity criterion is a voting system criterion used to analyze both single and multiple winner voting systems. A voting system is monotonic if it satisfies one of the definitions of the monotonicity criterion, given below.Douglas R...	Condorcet Condorcet criterion The Condorcet candidate or Condorcet winner of an election is the candidate who, when compared with every other candidate, is preferred by more voters. Informally, the Condorcet winner is the person who would win a two-candidate election against each of the other candidates...	Condorcet loser Condorcet loser criterion In single-winner voting system theory, the Condorcet loser criterion is a measure for differentiating voting systems. It implies the majority loser criterion....	Majority Majority criterion The majority criterion is a single-winner voting system criterion, used to compare such systems. The criterion states that "if one candidate is preferred by a majority of voters, then that candidate must win"....	Majority loser Majority loser criterion The majority loser criterion is a criterion to evaluate single-winner voting systems. The criterion states that if a majority of voters prefers every other candidate over a given candidate, then that candidate must not win....	Mutual majority Mutual majority criterion The mutual majority criterion is a criterion used to compare voting systems. It is also known as the majority criterion for solid coalitions and the generalized majority criterion...	Smith Smith criterion The Smith criterion is a voting systems criterion defined such that its satisfaction by a voting system occurs when the system always picks the winner from the Smith set, the smallest set of candidates such that every member of the set is pairwise preferred to every candidate not in the set...	ISDA	Clone independence Independence of clones criterion In voting systems theory, the independence of clones criterion measures an election method's robustness to strategic nomination. Nicolaus Tideman first formulated the criterion, which states that the addition of a candidate identical to one already present in an election will not cause the winner...	Reversal symmetry Reversal symmetry Reversal symmetry is a voting system criterion which requires that if candidate A is the unique winner, and each voter's individual preferences are inverted, then A must not be elected. Methods that satisfy reversal symmetry include Borda count, the Kemeny-Young method, and the Schulze method...	Polynomial time	Participation Participation criterion The participation criterion is a voting system criterion. It is also known as the "no show paradox". It has been defined as follows:* In a deterministic framework, the participation criterion says that the addition of a ballot, where candidate A is strictly preferred to candidate B, to an existing... , Consistency Consistency criterion A voting system is consistent if, when the electorate is divided arbitrarily into two parts and separate elections in each part result in the same choice being selected, an election of the entire electorate also selects that alternative...	Later no harm 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...
Schulze Schulze method The Schulze method is a voting system developed in 1997 by Markus Schulze that selects a single winner using votes that express preferences. The method can also be used to create a sorted list of winners...
Ranked pairs Ranked Pairs Ranked pairs or the Tideman method is a voting system developed in 1987 by Nicolaus Tideman that selects a single winner using votes that express preferences. RP can also be used to create a sorted list of winners....
Kemeny-Young
Nanson Nanson's method The Borda count can be combined with an Instant Runoff procedure to create hybrid election methods that are called Nanson method and Baldwin method.- Nanson method :The Nanson method is based on the original work of the mathematician Edward J...
Baldwin
AV/IRV 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...
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...
Bucklin Bucklin voting Bucklin voting is a class of voting systems that can be used for single-member and multi-member districts. It is named after its original promoter, James W. Bucklin of Grand Junction, Colorado, and is also known as the Grand Junction system...
Coombs Coombs' method The Coombs' method is a voting system created by Clyde Coombs used for single-winner elections in which each voter rank the candidates in order of preference. It is very similar to instant-runoff voting , a more common preferential voting system.-Procedures:Each voter rank-orders all of the...
MiniMax Minimax Condorcet In voting systems, the Minimax method is one of several Condorcet methods used for tabulating votes and determining a winner when using preferential voting in a single-winner election...
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...
Anti-plurality Anti-plurality voting Anti-plurality voting describes a voting method in which each voter votes against a single candidate, and the candidate with the fewest votes against wins. Anti-plurality voting is an example of a positional voting method.- An Example :...
Contingent voting Contingent vote The contingent vote is an electoral system used to elect a single winner, in which the voter ranks the candidates in order of preference. In an election, if no candidate receives an absolute majority of first preference votes, then all but the two leading candidates are eliminated and there is a...
Sri Lankan contingent voting
Supplementary voting