Dark horse

Meaning

A candidate or competitor who is little known but suddenly wins or shows great potential. It refers to an underdog who has been hiding their talents until the perfect moment.

Observant, optimistic

Used in a sentence

• Everyone expected the incumbent to win, but the dark horse took the election by a landslide.
• Keep an eye on the intern because he is a dark horse in this project.
• I bet on the dark horse because the odds were too good to pass up.