The U.S. Senate is the upper house of the Congress of the United States. It consists of two senators from every state (unlike the House of Representatives, whose members are apportioned according to the population of each state). The Senate has 100 members. As of January 2015 (the 114th Congress), the Senate included 54 Republicans, 44 Democrats, and 2 independents who caucus with the Democrats.
Senators serve 6-year terms, with a third of the terms expiring every 2 years. Originally, the Constitution provided for their selection by the state legislatures, in contrast to the popular election of members of the House. The 17th Amendment, adopted in 1913, required that senators be elected by the people. Senators must be 30 years of age, citizens of the United States for at least 9 years, and residents of the states they represent.
With the exception of four years (1947–48 and 1953–54), the Democrats controlled the Senate from 1933 through 1980. Since then, power has changed hands more often. Republicans controlled the chamber in 1981–86, 1995–2006 (except May 2001–December 2002), and 2015– . Democrats controlled it in 1987–94, May 2001–December 2002, and 2007–14. Unfortunately, the uncertainty of power in the more recent period (together with other factors) appears to have contributed to a growing dysfunction. When there was little doubt about continued party control, at least some politicians were willing to cooperate across party lines to achieve common goals. As the possibility of gaining power in the next election became more real, the minority party lost its incentive to cooperate in ways that might accrue to the advantage of the majority party. Obstruction for its own sake became a goal. Thus, recent years have been marked by political maneuvering and legislative stalemate.