<P> The history of the constitutional option can be traced to a 1917 opinion by Senator Thomas J. Walsh (Democrat of Montana). Walsh contended that the U.S. Constitution provided the basis by which a newly commenced Senate could disregard procedural rules established by previous Senates, and had the right to choose its own procedural rules based on a simple majority vote despite the two - thirds requirement in the rules . "When the Constitution says,' Each House may determine its rules of proceedings,' it means that each House may, by a majority vote, a quorum present, determine its rules," Walsh told the Senate . Opponents countered that Walsh's constitutional option would lead to procedural chaos, but his argument was a key factor in the adoption of the first cloture rule later that year . </P> <P> In 1957, Vice President Richard Nixon (and thus President of the Senate) wrote an advisory opinion that no Senate may constitutionally enact a rule that deprives a future Senate of the right to approve its own rules by the vote of a simple majority . (Nixon made clear that he was speaking for himself only, not making a formal ruling .) Nixon's opinion, along with similar opinions by Hubert Humphrey and Nelson Rockefeller, has been cited as precedent to support the view that the Senate may amend its rules at the beginning of the session with a simple majority vote . </P> <P> The option was officially moved by Senator Clinton P. Anderson (D - NM) (1963), Senator George McGovern (D - SD) (1967), and Senator Frank Church (D - ID) (1969), but was each time defeated or tabled by the Senate . </P> <P> A series of votes in 1975 have been cited as a precedent for the nuclear option, although some of these were reconsidered shortly thereafter . According to one account, the option was arguably endorsed by the Senate three times in 1975 during a debate concerning the cloture requirement . A compromise was reached to reduce the cloture requirement from two - thirds of those voting (67 votes if 100 Senators were present) to three - fifths of the current Senate (60 votes if there were no current vacancies) and also to approve a point of order revoking the earlier three votes in which the Constitutional option had been invoked . (This was an effort to reverse the precedent that had been set for cloture by majority vote). </P>

What does it mean when congress votes present