A dark horse

Also found in: Idioms.
References in periodicals archive ?
Why is a candidate for office who isn't expected to win called a dark horse candidate?
Former Senator Panfilo Ping Lacson could be a dark horse if he decides to join the presidential race in 2016, acting Senate Minority Leader Vicente Tito Sotto III said on Wednesday.
Hollywood, CA, August 26, 2013 --(PR.com)-- Helen Darras, Licensor & Producer for a Dark Horse Comics Graphic Novel will be appearing as a guest in Wales at the Inaugural 2013 Cardiff Film & Comic Con, held August 31 - September 1.