<P> The Standing Rules of the United States Senate provide that no senator may make more than two speeches on a motion or bill on the same legislative day . (A legislative day begins when the Senate convenes and ends with adjournment; hence, it does not necessarily coincide with the calendar day .) The length of these speeches is not limited by the rules; thus, in most cases, senators may speak for as long as they please . Often, the Senate adopts unanimous consent agreements imposing time limits . In other cases (for example, for the Budget process), limits are imposed by statute . In general, however, the right to unlimited debate is preserved . </P> <P> The filibuster is an obstructionary tactic used to defeat bills and motions by prolonging debate indefinitely . A filibuster may entail, but does not actually require, long speeches, dilatory motions, and an extensive series of proposed amendments . The longest filibuster speech in the history of the Senate was delivered by Strom Thurmond, who spoke for over twenty - four hours in an unsuccessful attempt to block the passage of the Civil Rights Act of 1957 . The Senate may end a filibuster by invoking cloture . In most cases, cloture requires the support of three - fifths of the Senate; however, if the matter before the Senate involves changing the rules of the body, a two - thirds majority is required . Cloture is invoked very rarely, particularly because bipartisan support is usually necessary to obtain the required supermajority . If the Senate does invoke cloture, debate does not end immediately; instead, further debate is limited to thirty additional hours unless increased by another three - fifths vote . </P> <P> When debate concludes, the motion in question is put to a vote . In many cases, the Senate votes by voice vote; the presiding officer puts the question, and Members respond either "Aye!" (in favor of the motion) or "No!" (against the motion). The presiding officer then announces the result of the voice vote . Any senator, however, may challenge the presiding officer's assessment and request a recorded vote . The request may be granted only if it is seconded by one - fifth of the senators present . In practice, however, senators second requests for recorded votes as a matter of courtesy . When a recorded vote is held, the clerk calls the roll of the Senate in alphabetical order; each senator responds when his or her name is called . Senators who miss the roll call may still cast a vote as long as the recorded vote remains open . The vote is closed at the discretion of the presiding officer, but must remain open for a minimum of 15 minutes . If the vote is tied, the Vice President, if present, is entitled to a casting vote . If the Vice President is not present, however, the motion is resolved in the negative . </P> <P> On occasion, the Senate may go into what is called a secret, or closed session . During a closed session, the chamber doors are closed, and the galleries are completely cleared of anyone not sworn to secrecy, not instructed in the rules of the closed session, or not essential to the session . Closed sessions are quite rare, and are usually held only under certain circumstances where the Senate is discussing sensitive subject - matter such as information critical to national security, private communications from the President, or even to discuss Senate deliberations during impeachment trials . Any Senator has the right to call a closed session as long as the motion is seconded . </P>

When is the president of the senate allowed to vote