Cooper was opposed in his re-election bid by Democratic Congressman Virgil M. Chapman, an ally of Earle C. Clements, who had been elected governor in 1947. As one of only a few Democrats who had voted in favor of the Taft–Hartley Act, Chapman had lost the support of organized labor, a key constituency for the Democrats. The Democratic-leaning "Louisville Times" endorsed Cooper, but the presence of Kentucky's favorite son, Alben Barkley, on the ballot as Harry S. Truman's running mate in the 1948 presidential election ensured a strong Democratic turnout in the state. Both Barkley and Clements stressed party unity during the campaign, and although Cooper polled much better than the Republican presidential ticket, he ultimately lost to Chapman in the general election by 24,480 votes.