state, using forms such as "the senior senator from Virginia" or "the junior senator from California". There are very few restrictions on the content of speeches, and there is no requirement that speeches be germane to the matter before the Senate. The Senate Rules 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 when it adjourns; 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. Filibuster 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. 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. Closed session 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 rare and are usually held only under certain circumstances in which the Senate is discussing sensitive subject matter, such as information critical to national security, private communications from the president, or discussions of Senate deliberations during impeachment trials. Any Senator has the right to call a closed session as long as the motion is seconded. Voting When debate concludes, the motion in