In politics, a front-runner (also spelled frontrunner or front runner) is a leader in an electoral race. While the front-runner in athletic events (the namesake of the political concept) is generally clear, a political front-runner, particularly in the presidential primary process, is less so as a potential nominee may lead in the polls, have the most name recognition, the most funds raised, or a combination of these. The front-runner is most often declared by the media who are following the race and is written about in a different style than his or her challengers.

The word front-runner originated in the United States. The term emerged from foot racing. It was used by 1914. According to Merriam-Webster the term meant "a contestant who runs best when in the lead" by that time. However the Dictionary of American Slang says it meant "the leader in a contest, election, etc." by that year.

The adjective front-running was used by 1940. It also originated from racing. The meaning of the word was analogous to its nounal counterpart at that time. The term was used as a noun by 1970 in the United States to mean "support given to a person or team only when they are doing well." By the 1980s a new definition for front-running emerged from the commodities market in which the word was also used as a noun. The definition was used to describe "a type of fraud in which a trader withholds a large customer order so that he can personally profit from its effect on the market."

The intransitive verb front-run emerged by 1950. It originated from a back formation of front-runner. By that year it had a meaning that was analogous to its nounal counterpart.

The related word frontrunneritis was used by 1995. It is a combination of frontrunner and –itis, a suffix frequently used informally to describe a tendency or mood that is comparable to a disease. The term was used by that time to describe "the condition of being a leading candidate." In particular it was used to characterize "a tendency to coast or to be under increased scrutiny by the press."

American author, columnist, journalist and presidential speechwriter William Safire describes the front-runner as being able to leave "the starting gate well" and set the pace for the other contestants. He uses the racing term "shows early foot" to characterize this tendency. Safire says occasionally the front-runner's lead becomes "insurmountable." He cites Barry Goldwater's successful 1964 Republican presidential nomination and Jimmy Carter's success in several convention states and early primaries in his 1976 presidential campaign as examples.

However Safire says the modern usage of the word front-runner has "ominous overtones" of being likely to eventually lose. As an example he references Franklin D. Roosevelt's receiving a letter from Robert W. Woolley about Roosevelt's front-runner status early in his 1932 presidential campaign: "Herein lies the danger ... automatically you become the target of the other candidates, real and potential. There isn't a single favorite son whose delegation won't be held out of the Roosevelt column so long as there is a reasonable chance of getting something for that favorite son, even at your expense." Safire gives another example when he quotes Ted Sorensen's thoughts about John F. Kennedy's front-runner status during his 1960 presidential campaign: "There were disadvantages in being the 'front runner.' The Senator's critics became more open and vocal and his every word was politically interpreted."

The outcome of the second round of primaries is critical to a front-runner's success. Safire argues that the front-runner "must come thundering into the convention increasing his speed and with enough 'kick' left for a final spurt" to be successful. He quotes Thomas E. Dewey writing about his losing the 1940 Republican presidential nomination as an example: "When the balloting starts, every candidate wants to show enough strength to be one of the leaders on the first ballot. He also wants to have enough strength in reserve so he can gain on the psychologically important second ballot. For example, in 1940, I led on the first three ballots out of six—the wrong three. I lost ground on the second ballot. That was the beginning of the end and everybody knew it."