A wonderful story is told about a swift,
coal-black horse named Dusky Pete who belonged to Tennessean Sam Flyn. Sam
made an east living riding his horse from town to town and entering him in
local races because Dusky Pete looked like a lame plug but he always won
handily. Sam would then collect his bets and go on to his next conquest.
But this story is a fable as far as scholars are concerned. Dark Horse was
first recorded in England, not America, in about 1830. Benjamin Disraeli
used it in his The Young Duke (1831) as a racing term that indicated more
than the color of the horse. “A dark horse, which has never been thought
of, rushed past the grand stand in sweeping triumph.” Given Disraeli’s
widespread popularity as a novelist and public figure, it wasn’t very long
before the term was introduced in American politics to describe a
candidate about whom little is known or one who wins unexpectedly. The
Democratic convention of 1844 produced the first political dark horse in
James Polk, who went on to become president, and the term was widely used
by 1865.