The Twelfth Amendment requires each elector to cast one vote for president and another vote for vice president. In each state and the District of Columbia, electors are chosen every four years on the Tuesday after the first Monday in November, and then meet to cast ballots on the first Monday after the second Wednesday in December. The candidates who receive a majority of electoral votes among the states are elected president and vice president of the United States when the Electoral College vote is certified by Congress in early January. Pursuant to the Twentieth Amendment, the terms for president and vice president end at noon on January 20 following an election for those offices; the new terms for those offices then begin.
Each state chooses electors, equal in number to that state's combined total of senators and representatives. There are a total of 538 electors, corresponding to the 435 representatives and 100 senators, plus the three electors for the District of Columbia as provided by the Twenty-third Amendment. The Constitution bars any federal official, elected or appointed, from being an elector. The Office of the Federal Register is charged with administering the Electoral College. Since the mid-19th century when all electors have been popularly chosen, the Electoral College has elected the candidate who received the most popular votes nationwide, except in four elections: 1876, 1888, 2000, and 2016. In 1824, there were six states in which electors were legislatively appointed, rather than popularly elected, so the true national popular vote is uncertain; the electors failed to select a winning candidate, so the matter was decided by the House of Representatives.
All states except California (before 1913), Maine, and Nebraska have chosen electors on a "winner-take-all" basis since the 1880s. Under the winner-take-all system, the state's electors are awarded to the candidate with the most votes in that state, thus maximizing the state's influence in the national election. Maine and Nebraska use the "congressional district method," selecting one elector within each congressional district by popular vote and awarding two electors by a statewide popular vote. Although no elector is required by federal law to honor his pledge, there have been very few occasions when an elector voted contrary to a pledge, and never once has it impacted the final outcome of a national election.
If no candidate for president receives a majority of electoral votes for president, the Twelfth Amendment provides that the House of Representatives will select the president, with each of the fifty state delegations casting one vote. If no candidate for vice president receives a majority of electoral votes for vice president, then the Senate will select the vice president, with each of the 100 senators having one vote.
The Constitutional Convention in 1787 used the Virginia Plan as the basis for discussions, as the Virginia delegation had proposed it first. The Virginia Plan called for the Congress to elect the president. Delegates from a majority of states agreed to this mode of election. However, a committee formed to work out various details including the mode of election of the president, recommended instead the election be by a group of people apportioned among the states in the same numbers as their representatives in Congress (the formula for which had been resolved in lengthy debates resulting in the Connecticut Compromise and Three-Fifths Compromise), but chosen by each state "in such manner as its Legislature may direct." Committee member Gouverneur Morris explained the reasons for the change; among others, there were fears of "intrigue" if the president were chosen by a small group of men who met together regularly, as well as concerns for the independence of the president if he were elected by the Congress. However, once the Electoral College had been decided on, several delegates (Mason, Butler, Morris, Wilson, and Madison) openly recognized its ability to protect the election process from cabal, corruption, intrigue, and faction. Some delegates, including James Wilson and James Madison, preferred popular election of the executive. Madison acknowledged that while a popular vote would be ideal, it would be difficult to get consensus on the proposal given the prevalence of slavery in the South:
There was one difficulty however of a serious nature attending an immediate choice by the people. The right of suffrage was much more diffusive in the Northern than the Southern States; and the latter could have no influence in the election on the score of Negroes. The substitution of electors obviated this difficulty and seemed on the whole to be liable to the fewest objections.
The Convention approved the Committee's Electoral College proposal, with minor modifications, on September 6, 1787. Delegates from states with smaller populations or limited land area such as Connecticut, New Jersey, and Maryland generally favored the Electoral College with some consideration for states. At the compromise providing for a runoff among the top five candidates, the small states supposed that the House of Representatives with each state delegation casting one vote would decide most elections.