The 1940 United States Senate elections coincided with the election of Franklin D. Roosevelt to his third term as president. The 32 seats of Class 1 were contested in regular elections, and special elections were held to fill vacancies. Although Roosevelt was re-elected, support for his administration had dropped somewhat after eight years, and the Republican opposition gained three seats from the Democrats. However, the New Deal Democrats regained firm control of both the House and Senate because Progressives dominated the election. The Minnesota Farmer–Labor Party also disappeared from the Senate, as Henrik Shipstead joined the Republican party and Ernest Lundeen had died during the preceding term. Senator Harry S. Truman of Missouri was elected to his final term in the Senate in 1940. Truman resigned in 1945 to serve as President Roosevelt's third Vice President. Republicans later gained an additional seat through an appointment in Colorado.

Gains, losses, and holds

Retirements

One Republican and two Democrats retired instead of seeking re-election. One Republican retired instead of seeking election to finish the unexpired term.

Defeats

Five Democrats and two Republicans sought re-election but lost in the primary or general election. One Democrat sought election to finish the unexpired term but lost in the general election.

Post-election changes

Party switches

One Farmer-Labor senator was re-elected as a Republican.

Change in composition

Before the elections

Election results

Race summaries

Special elections during the 76th Congress

In these special elections, the winner elected during 1940 and seated once qualified; ordered by election date.

Races leading to the 77th Congress

In these regular elections, the winners were elected for the term beginning January 3, 1941; ordered by state. All of the elections involved the Class 1 seats.

Closest races

Thirteen races had a margin of victory under 10%: There is no tipping point state.

Arizona

California

Connecticut

Delaware

Florida

Idaho (special)

Illinois (special)

Indiana

Kentucky (special)

Maine

Maryland

Massachusetts

Michigan

Minnesota

Mississippi

Missouri

One-term Democrat Harry S. Truman was narrowly re-elected. He would only serve until resigning January 17, 1945, to become U.S. Vice President.

Montana

Nebraska

Nevada

Pittman suffered a severe heart attack just before the election on November 5, and two doctors told his aides before the election that death was imminent. To avoid affecting the election, the party told the press that the senator was hospitalized for exhaustion and that his condition was not serious. Pittman died on November 10 at the Washoe General Hospital in Reno, Nevada. Governor Edward Carville would go on to appoint Berkeley L. Bunker as his replacement. In later years, a myth spread that Pittman had in fact died before the election, and his body had been kept on ice in the Mizpah Hotel in Tonopah so that Carville could appoint his replacement.

New Jersey

New Mexico

New York

The whole ticket nominated by Democrats and American Laborites was elected.

North Dakota

Ohio

Pennsylvania

Rhode Island

Tennessee

Texas

Utah

Vermont

There were 2 elections due to the June 20, 1940, death of two-term Republican Ernest Willard Gibson.

Vermont (regular)

Two-term Republican Warren Austin was easily re-elected. He faced no opponents in the primary. Austin served only until his August 2, 1946, resignation to become U.S. Ambassador to the United Nations.

Vermont (special)

Gibson's son, Republican Ernest W. Gibson Jr. was appointed June 24, 1940, to continue his father's term, pending a special election, in which he was not a candidate. Aiken did not take the seat until January 10, 1941, as he wanted to remain Governor of Vermont. He would be repeatedly re-elected and serve until his 1975 retirement.

Virginia

Washington

West Virginia

Wisconsin

Wyoming