<P> The United States Electoral College is a body of electors established by the United States Constitution, constituted every four years for the sole purpose of electing the president and vice president of the United States . The College consists of 538 electors, and an absolute majority of 270 electoral votes is required to win election . Pursuant to Article II, Section 1, Clause 2, the legislature of each state determines the manner by which its electors are chosen . Each state's number of electors is equal to the combined total of the state's membership in the Senate and House of Representatives; currently there are 100 senators and 435 representatives . Additionally, the Twenty - third Amendment provides that the District of Columbia is entitled to the number of electors no greater than that of the least populous state (i.e., 3). </P> <P> Any federal official, elected or appointed, is prohibited from being an elector . The Office of the Federal Register is charged with administering the Electoral College . Historically, the state legislatures chose the electors in more than half the states . That practice changed during the early 19th century, as states extended the right to vote to wider segments of the population . By 1832, all but one state (South Carolina) transitioned to popular election . Since 1864, the electors in every state have been chosen based on a popular election held on Election Day . The popular election for electors means the president and vice president are in effect chosen through indirect election by the citizens . 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 . </P>

Where does the number 538 come from in the electoral college
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