| 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. |

| dark horse n.
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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.
dark horse
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dark horse
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.