Since the mid-19th century most representatives have been members of the Democratic or Republican parties. The larger of the two groups at any given time is called the majority party and has primary responsibility for organizing the House.
The presiding officer of the House is the Speaker, who is traditionally the leader of the majority party. The Speaker is elected at the beginning of each 2-year term of Congress by the full membership of the House. Some Speakers have been vested with great formal powers that enabled them to dominate the House. Among the most powerful Speakers were Thomas Brackett Reed of Maine (1889–91, 1895–99) and Joseph G. Cannon of Illinois (1903–11). After Cannon, the formal authority granted to Speakers became more limited. Widely regarded as the most effective recent Speaker was Sam Rayburn of Texas, who served more years (1940–47, 1949–53, 1955–61) than any other Speaker. Newt Gingrich of Georgia (1995–98) sought to recentralize power in the Speaker's position. Nancy Pelosi of California (2007–10) was the first woman to hold this post.
Other important leaders of the House are the majority and minority floor leaders and their deputies, the majority and minority whips. Floor leaders are elected at the beginning of each new Congress by the members of their own parties. Their primary responsibilities are to set the agenda, to schedule the business of the House, and to facilitate the formation of legislative coalitions on individual bills and amendments. Traditionally, party discipline was not strictly enforced, and members often crossed party lines to support or oppose legislation. Since the late 20th century, parties have become more polarized and cross-party voting has become less common.
The most important decision-making units within the House are its committees. In 2015 the House had 20 standing committees; a permanent select committee on intelligence; a select committee to investigate the 2012 attack on the U.S. diplomatic mission in Benghazi, Libya; and 4 joint committees (with the U.S. Senate). These panels had various subcommittees that handled most of the initial work of studying and drafting legislation. Members are assigned to committees by their parties, and the partisan division on each such body usually reflects the party ratio within the House as a whole.
For most of the 20th century, the House followed the rule of seniority in selecting committee chairpersons—that is, the member of the majority party with the longest continuous service on each committee automatically became its chairperson. The Democrats modified this system in the early 1970s; all majority party members were permitted to participate by secret ballot in selecting committee chairpersons. After Republicans became the majority party in 1995, they set term limits for committee chairpersons at 6 years, and in 2001, 13 House committees gained new leaders. The Democrats have not adopted that rule, which they see as undermining institutional memory.
The House establishes the rules of its own proceedings at the beginning of each new Congress. The Speaker, as presiding officer, is the principal arbiter of the rules and is assisted by the House parliamentarian, who is an appointed official. A majority of the members may overrule the Speaker's interpretations or applications of the procedural rules.
Any member of the House may introduce legislation, usually called a bill. Bills are referred to appropriate committees by the Speaker, following precedent. Committees and subcommittees hold public hearings on some bills and prepare them for consideration by the full House. Debate on the House floor is regulated by the Committee on Rules, which recommends the length of time to be devoted to each bill and the conditions under which amendments may be considered. The recommendations of the Committee on Rules must be approved by the full House before a bill is debated. At the close of the time allotted for debate and amendment, the full House votes on a bill, usually by a recorded roll call.