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

After more than a century of false starts, the dark horse of the renewable-energy industry seems finally poised to make a significant dent in America’s insatiable appetite for new sources of power.

From The Wall Street Journal • Oct. 23, 2025

Beyond that core group, there’s still room for a dark horse to emerge — a scenario that could work in Reed’s favor, given his steady camp performance.

From Los Angeles Times • Aug. 22, 2025

By some accounts, he was a dark horse in a conclave race which many predicted would deliver unto us a Pope Pizzaballa.

From Salon • May 10, 2025

He found the dark horse in the night and stood caressing the warm skin, thick bristly mane, feeding sugar, talking.

From "The Killer Angels: The Classic Novel of the Civil War" by Michael Shaara

Related Words

• also-ran
• long shot
• sleeper
• underdog