 Bates was elected as a Democrat to the Seventy-fifth Congress to fill the vacancy caused by the resignation of Fred M. Vinson.He was reelected to the Seventy-sixth and to the six succeeding Congresses and served from June 4, 1938, to January 3, 1953.He was an unsuccessful candidate for renomination in 1952, and unsuccessfully sought the Democratic nomination in 1956 for the United States Senate.