 He was elected to the Senate in 1932, narrowly defeating Hiram Bingham III amidst the Democrat landslide that year, and served one term from March 4, 1933, to January 3, 1939.He was defeated for reelection by Republican John A. Danaher in 1938.Lonergan practiced law in Washington, D.C. until his death on October 18, 1947.