dark horse vs disputant

dark horse

noun
  • A candidate for an election who is nominated unexpectedly, without previously having been discussed or considered as a likely choice. 

  • Someone who possesses talents or favorable characteristics that are not known or expected by others. 

  • Used other than figuratively or idiomatically: see dark, horse. 

  • A horse whose capabilities are not known. 

disputant

adj
  • Disputing; engaged in controversy. 

noun
  • A participant in a dispute. 

How often have the words dark horse and disputant occurred in a corpus of books? (source: Google Ngram Viewer )