At the U.S. Open in 1936 at Baltusrol Golf Club in Springfield, New Jersey, Cooper was involved in a highly controversial showdown with Tony Manero, who was suspected of cheating. Manero defeated Cooper, who had already finished with a then-record score, by two shots to win the tournament; over the final holes, Manero was apparently receiving assistance in club selection from Gene Sarazen, a top player and fellow Italian-American, who had already finished his round. The Rules of Golf were later modified to prevent this, specifying automatic disqualification for a player who received advice from anyone except his caddie.