Politics in the United States have operated under a two-party system for virtually all of the country's history. For elective offices at all levels, state-administered primary elections are held to choose the major party nominees for subsequent general elections. Since the general election of 1856, the two dominant parties have been the Democratic Party, founded in 1824 (though its roots trace back to 1792), and the Republican Party, founded in 1854. Since the Civil War, only one third-party presidential candidate—former president Theodore Roosevelt, running as a Progressive in 1912—has won as much as 20% of the popular vote.
Within American political culture, the Republican Party is considered "center-right" or conservative and the Democratic Party is considered "center-left" or liberal. The states of the Northeast and West Coast and some of the Great Lakes states, known as "blue states" in political parlance, are relatively liberal-leaning. The "red states" of the South and the Rocky Mountains lean conservative. The current political culture is highly polarized.
The incumbent president, Republican George W. Bush, is the 43rd president in the country's history. All U.S. presidents to date have been white men. If Democrat Barack Obama wins the forthcoming presidential election, he will become the first African American president; if Republican John McCain wins, he will become the oldest man ever to ascend to the office, and his running mate, Sarah Palin, will become the first female vice president. Following the 2006 midterm elections, the Democratic Party controls both the House and the Senate. Every member of the U.S. Congress is a Democrat or a Republican except two independent members of the Senate—one (Joe Lieberman) a former Democratic incumbent, the other (Bernard Sanders) a self-described socialist. An overwhelming majority of state and local officials are also either Democrats or Republicans.