President of the United States(5)

Electoral College
Voters in each of the states elect a president on Election Day, set by law as the first Tuesday after the first Monday in November, once every four years; elections for other offices at all levels of government also occur on this date. Each state holds a number of electoral votes that correspond to electors in the Electoral College. Tickets of presidential and vice presidential candidates are shown on the ballot; each vote for the tickets actually corresponds to a vote for a slate of electors chosen by the candidates' political party. In most states, the ticket that wins the most votes in a state wins all of that state's electoral votes, and thus has their slate of electors chosen to vote in the Electoral College. Maine and Nebraska do not use this method, opting instead to give two electoral votes to the statewide winner and one electoral vote to the winner of each Congressional district. Neither state has split electoral votes between candidates as a result of this system in modern elections. In any case, the winning set of electors meets at their state's capital on the first Monday after the second Wednesday in December, a few weeks after the election, to vote, and sends a vote count to Congress.
The vote count is opened by the sitting vice president, acting in his capacity as President of the Senate, and read aloud to a joint session of the incoming Congress, which was elected at the same time as the president. Members of Congress can object to any state's vote count, provided that the objection is supported by at least one member of each house of Congress. A successful objection will be followed by debate; however, objections to the electoral vote count are rarely raised.
In the event that no candidate receives a majority of the electoral vote, the House of Representatives chooses the president from among the top three contenders. However, the House does not vote normally; instead, each state delegation is given only one vote, marginalizing the importance of more populous states. The vice president is chosen through normal voting in the Senate, where each state delegation is already of equal size.
Rationale
When the Constitution was written, the framers disagreed on the selection of the president: some favored national popular vote, while others wanted Congress to choose the president. The Electoral College was created as a compromise between the two proposals. It gave rural areas and smaller states a slightly larger role in determining the outcome of the election, and it continues to do so today; for example, the largest state by population, California, only has about one electoral vote for every 660,000 residents, while the smallest, Wyoming, has an electoral vote for about every 170,000.
Today, most of the electoral process is a formality in the public eye, as the choice of electors determines the result of the election, with a few exceptions. However, the Twelfth Amendment was written in a time when voters at large had little knowledge of candidates outside their state. As a result, the amendment accommodated this; the electors that voters had chosen were supposed to learn about the other candidates, and make an informed decision that represented the wishes of their constituents. Modern communication has rendered this unnecessary, and as a result, voters now choose between electors that are already pledged to a presidential candidate.
Source : http://en.wikipedia.org/wiki/President_of_the_United_States