The election of the president and vice president of the United States is an indirect election in which citizens of the United States who are registered to vote in one of the fifty U.S. states or in Washington, D.C., cast ballots not directly for those offices, but instead for members of the Electoral College. These electors then cast direct votes, known as electoral votes, for president and for vice president. The candidate who receives an absolute majority of electoral votes (at least 270 out of 538, since the Twenty-third Amendment granted voting rights to citizens of D.C.) is then elected to that office. If no candidate receives an absolute majority of the votes for president, the House of Representatives elects the president; likewise if no one receives an absolute majority of the votes for vice president, then the Senate elects the vice president.
United States presidential elections differ from many other republics around the world (operating under either the presidential system or the semi-presidential system) which use direct elections from the national popular vote ('one person, one vote') of their entire countries to elect their respective presidents. The United States instead uses indirect elections for its president through the Electoral College, and the system is highly decentralized like other elections in the United States. The Electoral College and its procedure are established in the U.S. Constitution by Article II, Section 1, Clauses 2 and 4; and the Twelfth Amendment (which replaced Clause 3 after its ratification in 1804). Under Clause 2, each state casts as many electoral votes as the total number of its Senators and Representatives in Congress, while (per the Twenty-third Amendment, ratified in 1961) Washington, D.C., casts the same number of electoral votes as the least-represented state, which is three. Also under Clause 2, the manner for choosing electors is determined by each state legislature, not directly by the federal government. Many state legislatures previously selected their electors directly, but over time all switched to using votes cast by state voters to choose the state's members of the electoral college (electors). Beyond the parameters set in the U.S. Constitution, state law, not federal, regulates most aspects of administering the popular vote, including most of the voter eligibility and registration requirements.
