In 1934, Pepper ran for the Democratic nomination for U.S. Senate, challenging incumbent Park Trammell. Pepper lost to Trammell in the primary runoff 51%–49%. But Pepper was unopposed in the 1936 special election following the death of Senator Duncan U. Fletcher, and succeeded William Luther Hill, who had been appointed pending the special election. In the Senate, Pepper became a leading New Dealer and close ally of President Franklin Delano Roosevelt. He was unusually articulate and intellectual, and, collaborating with labor unions, he was often the leader of the liberal-left forces in the Senate. His reelection in a heavily fought primary in 1938 solidified his reputation as the most prominent liberal in Congress. His campaign based on a wages-hours bill, which soon became the Fair Labor Standards Act of 1938. He sponsored the Lend-Lease Act. He filibustered an anti-lynching bill in 1937.