<P> It is not part of the US Constitution, becoming theoretically possible with a change of Senate rules only in 1806, and never being used until 1837 . Rarely used for much of the Senate's first two centuries, it was strengthened in the 1970s and in recent years, the majority has preferred to avoid filibusters by moving to other business when a filibuster is threatened and attempts to achieve cloture have failed . As a result, in recent decades this has come to mean that all major legislation (apart from budgets) now requires a 60% majority to pass . </P> <P> Under current Senate rules, any modification or limitation of the filibuster would be a rule change that itself could be filibustered, with two - thirds of those senators present and voting (as opposed to the normal three - fifths of those sworn) needing to vote to break the filibuster . However, under Senate precedents, a simple majority can (and has) acted to limit the practice by overruling decisions of the chair . The removal or substantial limitation of the filibuster by a simple majority, rather than a rule change, is called the constitutional option by proponents, and the nuclear option by opponents . </P> <P> On November 21, 2013, the Democratic controlled Senate voted 52 to 48 to require only a majority vote to end a filibuster of all executive and judicial nominees, excluding Supreme Court nominees, rather than the 3 / 5 of votes previously required . On April 6, 2017, the Republican controlled Senate voted 52 to 48 to require only a majority vote to end a filibuster of Supreme Court nominees . A 3 / 5 supermajority is still required to end filibusters on legislation . </P> <P> Only 13 state legislatures have a filibuster: </P>

A filibuster can be stopped when 3/5 of the senate votes for
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