Stassen's strongest bid for the Republican presidential nomination was in 1948, when he won a series of upset victories in early primaries. His challenge to the front runner, New York Governor and 1944 G.O.P. presidential nominee Thomas E. Dewey, was serious enough that Dewey challenged Stassen to a debate on the night before the Oregon Republican primary. The May 17 Dewey–Stassen debate was the first recorded modern debate between presidential candidates to take place in the United States. The debate, which concerned the criminalization of the Communist Party of the United States, was broadcast over the radio throughout the nation.