dark horse

American  

noun

1. a racehorse, competitor, etc., about whom little is known or who unexpectedly wins.

2. a candidate who is unexpectedly nominated at a political convention.

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dark horse British  

noun

1. a competitor in a race or contest about whom little is known; an unknown

2. a person who reveals little about himself or his activities, esp one who has unexpected talents or abilities

3. politics a candidate who is unexpectedly nominated or elected

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dark horse Cultural  

1. An unexpected winner. In politics, a dark horse is a candidate for office considered unlikely to receive his or her party's nomination, but who might be nominated if party leaders cannot agree on a better candidate.

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dark horse Idioms  

1. A little known, unexpectedly successful entrant, as in You never can tell—some dark horse may come along and win a Senate seat. This metaphoric expression originally alluded to an unknown horse winning a race and was so used in a novel by Benjamin Disraeli (The Young Duke, 1831). It soon began to be transferred to political candidates, among the first of whom was James K. Polk. He won the 1844 Democratic Presidential nomination on the eighth ballot and went on to win the election.

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Etymology

Origin of dark horse

First recorded in 1825–35

Example Sentences

That angst was a big reason why 64-year-old Sanae Takaichi surged from dark horse to Japan’s first female prime minister in October.

From Barron's • Jan. 8, 2026

Surprisingly, none of the three claimed Austen’s best-known novel, “Pride and Prejudice,” while dark horse candidate “Mansfield Park” — Austen’s far less sparkly, even somber third novel — appeared to win the day.

From Los Angeles Times • Dec. 30, 2025

At the same time, Darnold has emerged as both a dark horse to be this season’s MVP and an incredible bargain: His $33.5 million a year contract is far cheaper than the game’s highest-paid passers.

From The Wall Street Journal • Oct. 13, 2025

One dark horse is YouTube prankster Niko Omilana, says author Eloise Skinner, who holds a diploma in psychotherapy.

From BBC • May 14, 2025

He had become the convention's surprise dark horse.

From "Ambushed!" by Gail Jarrow

Related Words

• also-ran
• long shot
• sleeper
• underdog