Politics in the USA
The United States is a federation of 50 states plus the District of Columbia. Each state has considerable autonomy within the federation: each has its own state government, and laws differ in different states.
The Federal Government consists of the President and his administration acting as the executive body, with the US Congress acting as the legislative body. The President is elected indirectly by the people via an electoral college, and serves as both the Head of Government and Head of State.
The Congress is bicameral, comprising an upper house, known as the Senate, and a lower house, known as the House of Representatives. Both houses are directly elected by the people. While more seats are given to more populated states in the House of Representatives (eg. 53 for California, but only one for Alaska), the Senate is equally represented by each state, which each state getting two seats regardless of population. For presidential elections, the number of electoral votes assigned to each state is equal to the total number of representatives and senators from the state. The District of Columbia has no representation in either house of Congress, though it is given three electoral votes in Presidential elections.
American politics has been dominated by two political parties, the Democrats and the Republicans, since the 1860s. In recent years, the Democrats have been the party of the centre-left and the Republicans that of the centre-right. The current president, Barack Obama, is a Democrat; his predecessor, George W Bush (200-08) was a Republican; and Bush's predecessor, Bill Clinton (1992-2000) was a Democrat.