These staggered elections make for shifting alliances and may increase or decrease support for the president's policies. The bicameral division of Congress into two independent bodies "the House of Representatives and the Senate "also complicates the president's role. Traditionally, each body jealously guards its powers against executive interference. .
The parliamentary system. In such parliamentary democracies as the United Kingdom, the head of the government "the prime minister "faces fewer problems in organizing the government. The prime minister must be a member of Parliament and usually also is leader of the majority party in the House of Commons. The prime minister usually chooses a Cabinet from leaders of the majority party who are members of Parliament. .
In the United Kingdom, the prime minister and Cabinet thus have both executive and legislative authority. They are members of the legislature and responsible to it. If the prime minister's program fails to win parliamentary support, the opposition party may demand an election. This election is called for by the government but must occur within five years of the previous election. The people will vote either to keep the present government in power or to give the opposition party the opportunity to form a new government. .
Organizing the U.S. Congress. The Democratic and Republican parties organize their members in Congress according to the established structure of the House of Representatives and the Senate. At the beginning of each new session of Congress, both parties in the House and the Senate hold meetings to elect various officers and committee members. In the House, each party nominates a candidate for speaker, the body's presiding officer. But most representatives vote for their party's candidate, and so the majority party actually chooses the speaker. In the Senate, the vice president of the United States presides.