<P> Beginning with a rules change in 1806 , the Senate has traditionally not restricted the total time allowed for debate . In 1917 , Rule XXII was amended to allow for ending debate ( invoking `` cloture '' ) with a two - thirds majority , later reduced in 1975 to three - fifths of all senators `` duly chosen and sworn '' ( usually 60 ) . Thus , although a bill might have majority support , a minority of 41 or more senators can still prevent a final vote through endless debate , effectively defeating the bill . This tactic is known as a filibuster . </P>
<P> Beginning with a rules change in 1806 , the Senate has traditionally not restricted the total time allowed for debate . In 1917 , Rule XXII was amended to allow for ending debate ( invoking `` cloture '' ) with a two - thirds majority , later reduced in 1975 to three - fifths of all senators `` duly chosen and sworn '' ( usually 60 ) . Thus , although a bill might have majority support , a minority of 41 or more senators can still prevent a final vote through endless debate , effectively defeating the bill . This tactic is known as a filibuster . </P>
when did the senate changed to 60 votes
when did the senate changed to 60 votes
1975
1975