In 1958 McGee left the university to make his bid for the U.S. Senate, challenging incumbent Frank A. Barrett. He ran on a program of youth and new ideas. The race between McGee and Barrett attracted the attention of national party leaders on both sides. Senate Majority Leader Lyndon Johnson, Senator John F. Kennedy, Senator Wayne Morse of Oregon, Senator-elect Edmund Muskie of Maine, Congressman Joseph M. Montoya of New Mexico, and former President Harry S. Truman came to the state to support McGee, whose campaign slogan was "McGee for Me!". Lyndon Johnson pledged that, if Wyoming sent McGee to Washington, he would appoint him to the prestigious Appropriations Committee. Eleanor Roosevelt even conducted a national fund-raising drive for him. Barrett received assistance from national leaders as well, including Vice President Richard Nixon. McGee ultimately defeated Barrett by a margin of 1,913 votes out of a total of 116,230 votes cast in the election.