House and Senate party leaders are chosen in a before Congress meets.

The positions of party floor leaders are not included in the Constitution but developed gradually in the 20th century. The first floor leaders were formally designated in 1920 (Democrats) and 1925 (Republicans). The Senate Republican and Democratic floor leaders are elected by the members of their party in the Senate at the beginning of each Congress. Depending on which party is in power, one serves as majority leader and the other as minority leader. The leaders serve as spokespersons for their party's positions on issues. The majority leader schedules the daily legislative program and fashions the unanimous consent agreements that govern the time for debate. The majority leader has the right to be called upon first if several senators are seeking recognition by the presiding officer, which enables him to offer motions or amendments before any other senator. Elected at the beginning of each Congress by members of their respective party conferences to represent them on the Senate floor, the majority and minority leaders serve as spokesmen for their parties' positions on the issues. The majority leader has also come to speak for the Senate as an institution. Working with the committee chairs and ranking members, the majority leader schedules business on the floor by calling bills from the calendar and keeps members of his party advised about the daily legislative program. In consultation with the minority leader, the majority leader fashions unanimous consent agreements by which the Senate limits the amount of time for debate and divides that time between the parties. When time limits cannot be agreed on, the majority leader might file for cloture to shut off debate. Occupying the front desks on the center aisle, the two leaders coordinate party strategy and try to keep their parties united on roll-call votes. The leaders spend much of their time on or near the Senate floor, to open the day's proceedings, keep legislation moving, and protect the rights and interests of party members. When several senators are seeking recognition at the same time, the presiding officer in the Senate will call on the majority leader first, then on the minority leader, and then on the managers of the bill being debated, in that order. This right of first recognition enables the majority leader to offer amendments, substitutes, and motions to reconsider before any other senator. Former majority leader Robert C. Byrd called first recognition "the most potent weapon in the Majority Leader's arsenal." The posts of majority and minority leader are not included in the Constitution, as are the president of the Senate (the vice president of the United States) and the president pro tempore. Instead, party floor leadership evolved out of necessity. During the 19th century, floor leadership was exercised by the chair of the party conference and the chairs of the most powerful standing committees. In 1913, to help enact President Woodrow Wilson's ambitious legislative program, Democratic Conference chairman John Worth Kern of Indiana began functioning along the lines of the modern majority leader. In 1919, when Republicans returned to the majority, Republican Conference chairman Henry Cabot Lodge, Sr., also acted as floor leader. Not until 1925 did Republicans officially designate Senator Charles Curtis of Kansas as majority leader, separate from the conference chair. (Five years earlier, the Democrats had specifically named Oscar Underwood of Alabama as minority leader.) Although party floor leadership posts carry great responsibility, they provide few specific powers. Instead, floor leaders have largely had to depend on their individual skill, intelligence, and personality. Majority leaders seek to balance the needs of senators of both parties to express their views fully on a bill with the pressures to move the bill as quickly as possible toward enactment. These conflicting demands have required majority leaders to develop skills in compromise, accommodation, and diplomacy. Lyndon Johnson, who held the post in the 1950s, once said that the greatest power of the majority leader was "the power of persuasion." The majority leader usually works closely with the minority leader so that, as Senator Bob Dole explained, "we never surprise each other on the floor." The party leaders meet frequently with the president and with the leaders of the House of Representatives. The majority leader also greets foreign dignitaries visiting the Capitol.

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