Exaggerator has won the Preakness Stakes in Baltimore, shattering the dream of a US Triple Crown for Nyquist, which could only finish third.
Nyquist had won an emphatic victory in the first race in the series, the142nd Kentucky Derby.
But Exaggerator, ridden by Kent Desormeaux, produced a masterful display on a sodden course to overhaul the favourite on the home straight.
The third Triple Crown race, the Belmont Stakes, is on 11 June.
"I had a dream trip today,'' jockey Desormeaux said. "It was an amazing race and Exaggerator is an amazing horse.''
It was Nyquist's first taste of defeat after eight wins in a row.
The colt led the race from the start at Pimlico Race Course but faltered near the line and eventually finished third behind Cherry Wine.