In a tight race Thompson stunned the city by winning the election and becoming Rock Island's first Democratic mayor in 30 years.

Thompson, a New Deal Democrat, announced his candidacy for U.S. Congress in 1931 pledging to bring the nation out of the Great Depression.

With the aid of the New Deal and the help of Rock Island mayor Robert P. Galbraith, Thompson was able to secure funding for the construction of a new high school and a water treatment plant.

Thompson served in Congress for three terms before his defeat for reelection in 1938 by political newcomer Anton J. Johnson.

On November 15, 1939, former congressman Thompson was appointed president and chairman of the board of the Inland Waterways Corporation, and he served there until his resignation on August 15, 1944.