It’s what they DO when they DON’T want something to happen. Filibuster: An effort to prevent a vote in the U.S. Senate by extending debate. The Senate prides itself on being a deliberative body where debate is vital to decision-making. Senate rules allow debate on a measure to continue until three-fifths (60 of the 100 senators) vote to end it. At one time, a two-thirds vote was needed. But Senate rules changed in 1975. So, when a senator or group of senators want to block something, they take the floor and keep talking. In recent decades, the mere threat of a filibuster has been enough to halt action on almost any bill that lacks the support of 60 senators. But use of the filibuster was ended for approval of judicial appointments in 2013 and for Supreme Court approvals in 2017. The term filibuster is derived from a Dutch word for pirate. The record for the longest filibuster is held by Sen. Strom Thurmond of South Carolina, who spoke for 24 hours and 18 minutes in opposition to the Civil Rights Act of 1957.