Though plagued with ill health for much of his tenure as party chairman, Hannegan emphasized voter turnout efforts in Roosevelt's 1944 re-election campaign and prevented an upset by Thomas Dewey, who won a surprising 46 percent of the popular vote that year. He promoted a liberal policy agenda for the national party and was a strong advocate of labor unions. Hannegan stepped down as chairman after Democrats suffered Congressional losses in the 1946, the midterm elections, but his ideological focus at the helm of the party contributed to Truman's upset win in the Presidential election of 1948, and influenced his Fair Deal proposals.