After winning election to the Senate in 1938 over incumbent Democrat Robert J. Bulkley, Taft repeatedly sought the Republican presidential nomination, often battling for control of the party with the moderate faction of Republicans led by Thomas E. Dewey. He also emerged as a prominent non-interventionist and opposed U.S. involvement into World War II prior to the 1941 Japanese Attack on Pearl Harbor. Taft's non-interventionist stances damaged his 1940 candidacy, and the 1940 Republican National Convention nominated Wendell Willkie. Taft sought the presidency again in 1948, but he lost to Dewey at the 1948 Republican National Convention. He opposed the creation of NATO and criticized President Harry Truman's handling of the Korean War.