Front-runner is a term to describe the leader in a race, whether political or athletic. The term arose from the close symbolism between political campaigns and athletic running events. The term is used in the U.S. Presidential primary

United States presidential primary

The series of presidential primary elections and caucuses is one of the first steps in the process of electing the President of the United States of America. The primary elections are run by state and local governments, while caucuses are private events run by the political parties...

 process to label the potential nominee with the lead in the polls, the most name recognition, or most funds raised (or a combination of these).

The front-runner is most often anointed by the media

News media

The news media are those elements of the mass media that focus on delivering news to the general public or a target public.These include print media , broadcast news , and more recently the Internet .-Etymology:A medium is a carrier of something...

 who are following the race, and is written about in a different style than his or her challengers.

Front-runner can also be used to describe a type of sports fan

Fan (person)

A Fan, sometimes also called aficionado or supporter, is a person with a liking and enthusiasm for something, such as a band or a sports team. Fans of a particular thing or person constitute its fanbase or fandom...

 who likes only the team that is winning. Also known as a fairweather fan, the person will quickly, and repeatedly change allegiance

Bandwagon effect

The bandwagon effect is a well documented form of groupthink in behavioral science and has many applications. The general rule is that conduct or beliefs spread among people, as fads and trends clearly do, with "the probability of any individual adopting it increasing with the proportion who have...

with athletes and teams as teams and players become "good" or "bad" based on records.