The senators, two from each state, have six-year terms and were chosen by the state legislatures until 1913, when the Seventeenth Amendment, providing for their direct popular election, went into effect. Actually, many states, especially in the West, had already in effect adopted this reform through the use of the direct primary. The terms of one third of the senators expire every two years. A senator must be at least 30 years old, a U.S. citizen of not less than nine years standing, and a resident of the state in which he or she is elected. The Senate is presided over by the vice president of the United States, who has no part in its deliberations and may vote only in case of a tie; in his absence his duties are assumed by a president pro tempore, elected by the Senate.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.