The 1998 United States Senate elections were held on November 3 and seen as an even contest between the Republican Party and Democratic Party. While the Democrats had to defend more seats up for election, Republican attacks on the morality of President Bill Clinton failed to connect with voters and anticipated Republican gains did not materialize. The Republicans picked up open seats in Ohio and Kentucky and narrowly defeated Democratic incumbent Carol Moseley Braun (Illinois), but these were cancelled out by the Democrats' gain of an open seat in Indiana and defeats of Republican Senators Al D'Amato and Lauch Faircloth. The balance of the Senate remained unchanged at 55–45 in favor of the Republicans. With Democrats gaining five seats in the House of Representatives, this marked the first time since 1934 that the out-of-presidency party failed to gain congressional seats in a mid-term election, and the first time since 1822 that the party not in control of the White House failed to gain seats in the mid-term election of a President's second term. These are the last senate elections that resulted in no net change in the balance of power.
The 1986 United States Senate elections was an election for the United States Senate in the middle of Ronald Reagan's second presidential term. The Republicans had to defend an unusually large number of freshman Senate incumbents who had been elected on President Ronald Reagan's coattails in 1980. Democrats won a net of eight seats, defeating seven freshman incumbents and regaining control of the Senate for the first time since January 1981. The party not controlling the presidency gained seats, as usually occurs in mid-term elections.
The 1978 United States Senate elections in the middle of Democratic President Jimmy Carter's term. Thirteen seats changed hands between parties. The Democrats at first lost a net of two seats to the Republicans, and then one more in a special election. Democrats nevertheless retained a 58-41 majority.
The 1976 United States Senate elections was an election for the United States Senate that coincided with Democratic Jimmy Carter's presidential election and the United States Bicentennial celebration. Although almost half of the seats decided in this election changed parties, Carter's narrow victory did not provide coattails for the Democrats, and the balance of the chamber remained the same.
The 1970 United States Senate elections was an election for the United States Senate, taking place in the middle of Richard Nixon's first term as President. The Democrats lost a net of three seats, while the Republicans and the Conservative Party of New York picked up one net seat each, and former Democrat Harry F. Byrd Jr. was re-elected as an independent.
The 1964 United States Senate elections 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 2019, this is 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, convict and expel certain officials, or invoke cloture without any votes from Republicans. The Senate election 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. The Republicans gained one seat at the expense of the Democrats. The Democrats nonetheless retained a commanding lead in the Senate with 64 seats to 36. As Majority Leader Lyndon B. Johnson was elected Vice President, Mike Mansfield became the new Majority Leader.
The 1950 United States Senate elections occurred in the middle of Harry S. Truman's second term as President. As with most 20th-century second-term mid-terms, the party out of the Presidency made significant gains. The Republican opposition made a net gain of five seats, taking advantage of the Democratic administration's declining popularity during the Cold War and the aftermath of the Recession of 1949. The Democrats held a narrow 49 to 47 seat majority after the election. This became the first time since 1932 that the Senate Majority Leader lost his seat and the only instance where the majority leader lost his seat while his party retained the majority.
The 1946 United States Senate elections were held November 5, 1946, in the middle of Democratic President Harry S. Truman's first term.
The United States Senate elections of 1940 coincided with the election of Franklin D. Roosevelt to his third term as President.
The United States Senate elections of 1938 occurred in the middle of Franklin D. Roosevelt's second term. This occurred six years after the Democratic landslide in the 1932 election, and so the opposition Republicans gained seven seats from the Democrats. However, the Democrats retained a commanding lead over the Republicans with more than two-thirds of the chamber.
The United States Senate elections of 1936 coincided with the reelection of President Franklin D. Roosevelt. The Great Depression continued and voters backed progressive candidates favoring Roosevelt's New Deal in races across the country. The Democrats gained 5 net seats during the election, and in combination with Democratic and Farmer–Labor interim appointments and the defection of George W. Norris from the Republican Party to become independent, the Republicans were reduced to 16 seats, the most lopsided Senate since Reconstruction.
The elections for the United States House of Representatives were held on 5 November 2002, in the middle of President George W. Bush's first term. Although it was a midterm election, the Republican Party gained a net eight seats, solidifying their majority. Some speculate that this may have been due to increased support for the President's party in the wake of the September 11 attacks.
The 1934 United States House of Representatives elections were held in the middle of President Franklin D. Roosevelt's first term. The Democratic Party continued its progress, gaining another 9 net seats from the opposition Republican Party, who also lost seats to the Progressive Party. The Republicans were reduced below one-fourth of the chamber for the first time since the creation of the party. The Wisconsin Progressive Party, a liberal group which allied with the Democrats, also became a force in Wisconsin politics.
The 1948 United States elections was held on November 2, 1948. The election took place during the beginning stages of the Cold War. Democratic incumbent President Harry S. Truman was elected to a full term, defeating Republican nominee New York Governor Thomas E. Dewey and two erstwhile Democrats. The Republicans, who had just won both the House and the Senate two years earlier, ceded control of both chambers of Congress to the Democrats. Puerto Rico also elected Luis Muñoz Marín of the Popular Democratic Party as its first democratically elected governor.
The 2002 United States elections were held on November 5, in the middle of Republican President George W. Bush's first term. Unusual in midterm elections, the incumbent president's party gained seats in both chambers of the United States Congress. The Republicans picked up net gains of 2 Senate seats and 8 House seats.
The 1944 United States elections was held on November 7, 1944, taking place just a month after the Allies liberated Paris in World War II. President Franklin D. Roosevelt was re-elected to an unprecedented fourth term, while the Democrats retained their majorities in both chambers of Congress.
The 1946 United States elections were held on November 5, 1946, and elected the members of the 80th United States Congress. In the first election after the end of World War II, incumbent President Harry S. Truman and the Democratic Party suffered large losses. After having been in the minority of both chambers of Congress since 1932, Republicans took control of both the House and the Senate.
The 1934 United States elections were held on November 6, 1934. The election took place in the middle of Democratic President Franklin D. Roosevelt's first term, during the Great Depression. The Democrats built on the Congressional majorities they had won in the previous two elections. In the House of Representatives, Roosevelt's party gained nine seats, mostly from the Republican Party. The Democrats also gained nine seats in the U.S. Senate, thereby winning a supermajority. A Progressive also unseated a Republican in the Senate. This marked the first time since the Civil War that an incumbent president's party gained seats in a midterm election, followed by 1998, 2002 and 2018.
