1964 United States Senate elections

1964 United States Senate elections

← 1962 November 3, 1964 1966 →
35 of the 100 seats in the United States Senate 51 seats needed for a majority
Majority party Minority party   Leader Mike Mansfield Everett Dirksen Party Democratic Republican Leader since January 3, 1961 January 3, 1959 Leader's seat Montana Illinois Seats before 66 34 Seats after 68 32 Seat change 2 2 Popular vote 30,786,035[1][a] 23,171,991[1] Percentage 56.2% 42.3% Seats up 26 9 Races won 28 7
Results of the elections:      Democratic gain      Democratic hold      Republican gain      Republican hold      No election Rectangular inset (Tennessee): both seats up for election
Majority Leader before election Mike Mansfield Democratic Elected Majority Leader Mike Mansfield Democratic

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^[update], this was the last time either party has had a two-thirds majority in the Senate, which allowed the Senate Democrats to override a veto, propose constitutional amendments, or convict and expel certain officials without any votes from Senate Republicans. However, internal divisions would have prevented the Democrats from having done so. The Senate election cycle coincided with Democratic gains in the House in the same year.

In a close race in Nevada, Democratic incumbent Howard Cannon won re-election over Republican Lieutenant Governor Paul Laxalt by fewer than 100 votes. Laxalt joined Cannon in the Senate when he won Nevada's other seat in 1974. Patrick V. McNamara (D–Michigan) later died on April 30, 1966, and was replaced on May 11, 1966, by appointee Robert P. Griffin (R), reducing Democrats' majority to 67–33.

Notably, of the 35 seats up for election this year, 26 were held by Democrats, who managed to retain 25 of them. A party defending two-thirds of the seats up for election would not make net gains in the Senate again until 2012. Coincidentally, it would be the same Senate class, class 1. This is the earliest round of Senate elections in which a first-elected member is still alive (Fred Harris, D-OK).

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