The 1996 United States Senate elections were held on November 5, with the 33 seats of Class 2 contested in regular elections. Special elections were also held to fill vacancies. They coincided with the presidential election of the same year, in which Democrat Bill Clinton was re-elected president.
The 1990 United States Senate elections were held on Tuesday, November 6, 1990, with the 33 seats of Class 2 contested in regular elections. Special elections were also held to fill vacancies. The Democratic Party increased its majority with a net gain of one seat from the Republican Party. The election cycle took place in the middle of President George H. W. Bush's term, and, as with most other midterm elections, the party not holding the presidency gained seats in Congress.
The 1972 United States Senate elections were held on November 7, with the 33 seats of Class 2 contested in regular elections. They coincided with the landslide re-election of Republican President Richard Nixon. Despite Nixon's landslide victory, Democrats increased their majority by two seats. The Democrats picked up open seats in Kentucky and South Dakota, and defeated four incumbent senators: Gordon Allott of Colorado, J. Caleb Boggs of Delaware, Jack Miller of Iowa, and Margaret Chase Smith of Maine. The Republicans picked up open seats in New Mexico, North Carolina, and Oklahoma, and defeated one incumbent, William B. Spong Jr. of Virginia.
The 1966 United States Senate elections were elections on November 8, 1966, for the United States Senate which occurred midway through the second term of President Lyndon B. Johnson. The 33 seats of Class 2 were contested in regular elections. Special elections were also held to fill vacancies. With divisions in the Democratic base over the Vietnam War, and with the traditional mid-term advantage of the party not holding the presidency, the Republicans took three Democratic seats, thereby breaking Democrats' 2/3rds supermajority. Despite Republican gains, the balance remained overwhelmingly in favor of the Democrats, who retained a 64–36 majority. Democrats were further reduced to 63–37, following the death of Robert F. Kennedy in June 1968.
The 1964 United States Senate elections were held on November 3. The 33 seats of Class 1 were contested in regular elections. Special elections were also held to fill vacancies. They coincided with the election of President Lyndon B. Johnson by an overwhelming majority, to a full term. His Democratic Party picked up a net two seats from the Republicans. As of 2023, this was the last time either party has had a two-thirds majority in the Senate, which would have hypothetically allowed the Senate Democrats to override a veto, propose constitutional amendments, or convict and expel certain officials without any votes from Senate Republicans. In practice, however, internal divisions effectively prevented the Democrats from doing so. The Senate election cycle coincided with Democratic gains in the House in the same year.
The 1960 United States Senate elections coincided with the election of John F. Kennedy as president on November 8, 1960. The 33 seats of Class 2 were contested in regular elections. A special election was also held on June 28, 1960, for a mid-term vacancy in North Dakota where Democrats flipped a seat to expand their majority to 66–34. As Majority Leader Lyndon Johnson was elected Vice President, Mike Mansfield became the new majority leader.
The 1956 United States Senate elections were elections for the United States Senate that coincided with the re-election of President Dwight D. Eisenhower. The 32 seats of Class 3 were contested in regular elections, and three special elections were held to fill vacancies. Although Democrats gained two seats in regular elections, the Republicans gained two seats in special elections, leaving the party balance of the chamber unchanged.
The 1954 United States Senate elections was a midterm election in the first term of Dwight D. Eisenhower's presidency. The 32 Senate seats of Class 2 were contested in regular elections, and six special elections were held to fill vacancies. Eisenhower's Republican party lost a net of two seats to the Democratic opposition. This small change was just enough to give Democrats control of the chamber with the support of an Independent who agreed to caucus with them, he later officially joined the party in April 1955.
The 1948 United States Senate elections were elections which coincided with the election of Democratic President Harry S. Truman for a full term. The 32 seats of Class 2 were contested in regular elections, and one special election was held to fill a vacancy. Truman had campaigned against an "obstructionist" Congress that had blocked many of his initiatives, and in addition the U.S. economy recovered from the postwar recession of 1946–1947 by election day. Thus Truman was rewarded with a Democratic gain of nine seats in the Senate, enough to give them control of the chamber. This was the last time until 2020 that Democrats flipped a chamber of Congress in a presidential election cycle.
The 2014 United States Senate elections were held on November 4, 2014. A total of 36 seats in the 100-member U.S. Senate were contested. Thirty-three Class 2 seats were contested for regular six-year terms to be served from January 3, 2015, to January 3, 2021, and three Class 3 seats were contested in special elections due to Senate vacancies. The elections marked 100 years of direct elections of U.S. senators. Going into the elections, 21 of the contested seats were held by the Democratic Party, while 15 were held by the Republican Party.
The 1980 United States Senate election in Colorado was held on November 4, 1980. Incumbent Democratic U.S. Senator Gary Hart won re-election to a second term despite Republican nominee Ronald Reagan winning the state over Democratic President Jimmy Carter in the concurrent presidential election. This election was the first time since 1948 that an incumbent Democratic Senator from Colorado was re-elected or won re-election and the first time since 1938 that an incumbent Democratic Senator from Colorado was re-elected or won re-election for this seat.
The 1972 United States Senate election in Montana took place on November 7, 1972. Incumbent United States Senator Lee Metcalf, who was first elected to the Senate in 1960 and was re-elected in 1966, ran for re-election. After winning the Democratic primary, he moved on to the general election, where he faced Hank Hibbard, a State Senator and the Republican nominee. Following a close campaign, Metcalf managed to narrowly win re-election to his third term in the Senate over Hibbard. Montana was one of fifteen states alongside Alabama, Arkansas, Colorado, Delaware, Georgia, Iowa, Louisiana, Maine, Minnesota, Mississippi, New Hampshire, Rhode Island, South Dakota and West Virginia that were won by Republican President Richard Nixon in 1972 that elected Democrats to the United States Senate.
The 1942 United States Senate election in Colorado took place on November 3, 1942. Incumbent Democratic Senator Edwin C. Johnson was re-elected to second term over Republican Governor Ralph L. Carr.
The 1936 United States Senate election in Colorado took place on November 3, 1936. Incumbent Democratic Senator Edward P. Costigan did not seek a second term in office. Democratic Governor Ed Johnson won the open race to succeed him over Raymond L. Sauter.
The 1944 United States Senate special election in Colorado took place on November 7, 1944. Incumbent Republican Senator Eugene Millikin, who was first appointed to fill Alva B. Adams's seat in 1941 and re-elected at the ensuing special election in 1942, ran for re-election to his first full term. In the general election, he faced wealthy Denver attorney Barney L. Whatley. Millikin benefited from the strong Republican performance in Colorado—Thomas E. Dewey and Governor John C. Vivian both won their respective elections by decisive margins—and cruised to a landslide victory over Whatley.
The 1916 United States Senate election in Maine was held on September 11, 1916.
The 1914 United States Senate election in South Dakota took place on November 3, 1914. Incumbent Senator Coe I. Crawford, a Republican, sought re-election in his first popular election. He was defeated in the Republican primary by Congressman Charles H. Burke, the House Minority Whip. In the general election, he was narrowly defeated by Edwin S. Johnson, the 1912 Democratic nominee for Governor, who won a narrow plurality. Edwin Stockton Johnson became the first Democrat ever to have been elected to the United States Senate from South Dakota and the first non-Republican to have been elected to the United States Senate from South Dakota since James Henderson Kyle in 1897.
The 1920 United States Senate election in Colorado took place on November 2, 1920. Incumbent Democratic Senator Charles S. Thomas initially declined to run for re-election, and State Supreme Court Justice Tully Scott won the Democratic nomination to succeed him, facing off against former Leadville Mayor Samuel D. Nicholson, the Republican nominee. However, in October 1920, Thomas announced that he would run for re-election as the nominee of the National Party. However, Thomas's decision did not ultimately affect the outcome of the election. Aided by Republican presidential nominee Warren G. Harding's strong performance in the state, as well as Republican Governor Oliver Henry Shoup's landslide re-election, Nicholson defeated Tully and Thomas in a landslide. Out of four candidates, Thomas placed fourth, winning just 3% of the vote and finishing behind Farmer–Labor nominee G. F. Stevens.
The 1954 United States Senate election in Colorado took place on November 2, 1954. Incumbent Democratic Senator Edwin C. Johnson did not run for re-election, instead he gave up his seat to run for Governor again. Republican Lieutenant Governor Gordon Allott defeated Democratic U.S. Representative John A. Carroll in the race for the open seat.
The 2020 United States House of Representatives elections in Colorado was held on November 3, 2020, to elect the seven U.S. representatives from the state of Colorado, one from each of the state's seven congressional districts. The elections coincided with the 2020 U.S. presidential election, as well as other elections to the House of Representatives, elections to the United States Senate and various state and local elections.
