The election of the president and the 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 in turn 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 a total 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 chooses the winner; if no one receives an absolute majority of the votes for vice president, then the Senate chooses the winner.
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 of the states 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 of them switched to using the popular vote to determine electors, which persists today. Once chosen, electors generally cast their electoral votes for the candidate who won the plurality in their state, but 18 states do not have provisions that specifically address this behavior; those who vote in opposition to the plurality are known as "faithless" or "unpledged" electors. In modern times, faithless and unpledged electors have not affected the ultimate outcome of an election, so the results can generally be determined based on the state-by-state popular vote.
Presidential elections occur quadrennially with registered voters casting their ballots on Election Day, which since 1845 has been the first Tuesday after November 1. This date coincides with the general elections of various other federal, state, and local races; since local governments are responsible for managing elections, these races typically all appear on one ballot. The Electoral College electors then formally cast their electoral votes on the first Monday after December 12 at their respective state capitals. Congress then certifies the results in early January, and the presidential term begins on Inauguration Day, which since the passage of the Twentieth Amendment has been set at January 20.
The nomination process, consisting of the primary elections and caucuses and the nominating conventions, was not specified in the Constitution, but was developed over time by the states and political parties. These primary elections are generally held between January and June before the general election in November, while the nominating conventions are held in the summer. Though not codified by law, political parties also follow an indirect election process, where voters in the fifty states, Washington, D.C., and U.S. territories, cast ballots for a slate of delegates to a political party's nominating convention, who then in turn elect their party's presidential nominee. Each party may then choose a vice presidential running mate to join the ticket, which is either determined by choice of the nominee or by a second round of voting. Because of changes to national campaign finance laws since the 1970s regarding the disclosure of contributions for federal campaigns, presidential candidates from the major political parties usually declare their intentions to run as early as the spring of the previous calendar year before the election (almost 21 months before Inauguration Day).
