Senate Rules and Filibuster Aren't in the Constitution

Senate rules, and especially the rules about filibuster and debate, have changed a lot over our nation’s history.

1789 The original rules of the Senate included a provision that would allow debate to be cut off by a simple majority vote. And from 1789-1806, this provision was only used four times in the U.S. Senate.

1917 A procedure to cut off debate, known as “cloture,” was adopted. This rule required two-thirds (up to 67 votes) of the senators present and voting to agree.

1949 This rule was changed to require that two-thirds (a full 67 votes) of the full Senate had to vote to cut off debate. This was the start of record-setting filibusters, including Strom Thurmond’s marathon filibuster of the 1957 Civil Rights Act.

1959 The filibuster rule was changed back to require that two-thirds (up to 67 votes) of those senators voting and present was necessary to cut off debate.

1975 to present In 1975, the number of votes needed to cut off debate was changed to three-fifths of all senators, or 60 votes. This is the standard in place today.