dark horse

dark-horse的词性：
n.（名词）

1. One who achieves unexpected support and success as a political candidate, typically during a party's convention.
“黑马”候选人：作为政治候选人获得意外的支持和成功的人，尤其是在一政党的会议期间

2. A little-known, unexpectedly successful entrant, as in a horserace.
黑马：实力不为人所知却意外获胜的参赛者，如在赛马中