<P> Even though the aggregate national popular vote is calculated by state officials, media organizations, and the Federal Election Commission, the people only indirectly elect the president, as the national popular vote is not the basis for electing the president or vice president . The president and vice president of the United States are elected by the Electoral College, which consists of 538 presidential electors from the fifty states and Washington, D.C. Presidential electors are selected on a state - by - state basis, as determined by the laws of each state . Since the election of 1824, most states have appointed their electors on a winner - take - all basis, based on the statewide popular vote on Election Day . Maine and Nebraska are the only two current exceptions, as both states use the congressional district method . Although ballots list the names of the presidential and vice presidential candidates (who run on a ticket), voters actually choose electors when they vote for president and vice president . These presidential electors in turn cast electoral votes for those two offices . Electors usually pledge to vote for their party's nominee, but some "faithless electors" have voted for other candidates or refrained from voting . </P> <P> A candidate must receive an absolute majority of electoral votes (currently 270) to win the presidency or the vice presidency . If no candidate receives a majority in the election for president or vice president, the election is determined via a contingency procedure established by the Twelfth Amendment . In such a situation, the House chooses one of the top three presidential electoral vote - winners as the president, while the Senate chooses one of the top two vice presidential electoral vote - winners as vice president . </P> <P> A state's number of electors equals the number of representatives plus two electors for both senators the state has in the United States Congress . The number of representatives is based on the respective populations, determined every 10 years by the United States Census . Each representative represents on average 711,000 persons . </P> <P> Under the Twenty - third Amendment, Washington, D.C., is allocated as many electors as it would have if it were a state, but no more electors than the least populous state . The least populous state (which is Wyoming, according to the 2010 census) has three electors; thus, D.C. cannot have more than three electors . Even if D.C. were a state, its population would entitle it to only three electors; based on its population per electoral vote, D.C. has the second highest per capita Electoral College representation, after Wyoming . </P>

When does a state's number of representatives changed
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