Republican president Dwight D. Eisenhower convinced John Sherman Cooper, a former senator and ambassador who was immensely popular in Kentucky, to challenge Wetherby, hoping his presence on the ticket would aid his own re-election bid. In the Republican primary, voters chose Thruston B. Morton to challenge Clements. With two of his factional enemies as candidates for the Senate, Governor Chandler bolted the party and supported the Republican candidates. Further complicating Clements' campaign was the fact that Senate majority leader Lyndon Johnson suffered a heart attack in 1956, and as majority whip, Clements had to spend much of his time in Washington, D.C. covering Johnson's duties in the Senate. What time he was in Kentucky was usually devoted to Wetherby's campaign, since the Democrats believed Clements would be re-elected easily while Wetherby faced much stiffer odds. These factors, combined with the landslide of support for Eisenhower, the Republican presidential candidate, contributed to the defeat of both Wetherby and Clements. Cooper defeated Wetherby by 65,000 votes, while Clements lost to Morton by a margin of 7,000 votes out of more than 1 million that were cast in the election. It was Clements' first defeat for elected office in a career that spanned thirty years.