It takes 60 votes in the Senate to block a filibuster, or an unlimited debate. Senate rules allow any member or group of senators to speak as long as necessary on an issue. The only way to end the debate is to evoke "cloture," or win a vote of 60 members. Without the 60 votes needed, the filibuster can go on forever.
Senators have effectively used filibusters - or more often, the threat of a filibuster - to change legislation or block a bill from being voted on the Senate floor.
Sen. Strom Thurmond gave the longest filibuster in 1957, when he spoke for more than 24 hours against the Civil Rights Act. Sen. Huey Long would recite Shakespeare and read recipes to pass the time while filibustering in the 1930s.
But the most famous filibuster was conducted by Jimmy Stewart in the classic film Mr. Smith Goes to Washington.
Senators have used filibusters to push for changes in legislation, or to prevent a bill from passing with less than 60 votes. It is often a way for the minority party to yield power and block legislation, even though the majority party chooses what bills will get a vote.
Often, senators make their intent to filibuster known to other senators to prevent a bill from being scheduled for a vote. That's why you rarely see long filibusters on the Senate floors. Bills that will not be approved are rarely scheduled for a vote.
In the Bush administration, Democratic senators effectively filibustered against several judicial nominations. In 2005, a group of seven Democrats and seven Republicans - dubbed the "Gang of 14" - got together to reduce filibusters for judicial nominees. The Democrats agreed not to filibuster against several nominees, while Republicans ended efforts to rule filibusters unconstitutional.
Against the Filibuster
In recent months, some pundits have called for an end to filibusters, or to lower the threshold to 55 votes. They suggest the rule has been used to often in recent years to block important legislation. Rep. Alan Grayson (D-Fla.) has an online petition that says: "Until 1970, no session of Congress had more than ten votes on cloture to end a filibuster. Until 2007, the record was 58. But since Democrats regained control of the Senate, filibusters have skyrocketed. The last session had a new record of 112."
And, Grayson argues, the filibuster is not mentioned in the Constitution.