Filibuster in the United States Senate

A filibuster in the United States Senate is a dilatory or obstructive tactic used in the United States Senate to prevent a measure from being brought to a vote. The most common form of filibuster occurs when a senator attempts to delay or block a vote on a bill by extending debate on the measure. The Senate rules permit a senator, or a series of senators, to speak for as long as they wish, and on any topic they choose, unless "three-fifths of the Senators duly chosen and sworn" (usually 60 out of 100) bring the debate to a close by invoking cloture under Senate Rule XXII.

According to the Supreme Court's ruling in United States v. Ballin (1892), Senate rules can be changed by a simple majority vote. Nevertheless, under current Senate rules, a rule change could itself be filibustered, requiring two-thirds of senators who are present and voting to end debate. (This differs from the usual requirement for three-fifths of sworn senators.) Despite this written requirement, the Senate's presiding officer could, on motion, declare a Senate rule unconstitutional, and that decision could be upheld by a simple majority vote.

The concept of the filibuster emerged in the Senate in the 1850s. At the time, both the Senate and the House of Representatives allowed filibusters as a way to prevent a vote from taking place. Subsequent revisions to House rules limited filibuster privileges in that chamber, but the Senate continues to allow the tactic.

In 1789, the first U.S. Senate adopted rules allowing senators to move the previous question, which meant ending debate and proceeding to a vote. But in 1806, former Vice President Aaron Burr argued that the previous-question motion was redundant, had only been exercised once in the preceding four years, and should be eliminated. The Senate agreed and modified its rules. Because it created no alternative mechanism for terminating debate, filibusters became possible.

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