The US presidential election is an undirect election happening every 4 years. The Election day is scheduled in November on the tuesday following the 1st of November. In 2012, this is on the 6 of November.
What means an undirect election ?
215 millions of american citizens can vote for their president and their vice-president (the presidential ticket). They vote on the Election Day but their vote will designate an electoral college consisting in 538 Great Electors. These Great Electors will elect the president a few weeks later (on the 17th of December) but with the number of Great Electors for each candidates, we know on the Election Day who will be the next president and his vice-president. The Great Electors are not attributed nationally but for each state. Thus, it is an election state by state and not a national election. It means that a candidtae can be elected even if he has les vote in the whole country. It depends on his victory in each state and the number of Great Electors these state victories will bring him.
How are attributed Great Electors for each state ?
The number of Great Electors for each state is equal to the number of Congressmen attributed to each state (number of representatives depending on the population + 2 senators by state). 3 Great Electors are additionnalyy attributed to the Federal District of Columbia (Washington D.C.) whis is not a state and has no congressmen.
How are Great Electors votes attributed to the candidates ?
The system is the winner takes all. It means that when a candidate wins in a state (no matter what is the margin), he gets the whole great electors attributed to this state. Winning in the big states is a key. 2 exceptions : Nebraska attributes its 6 great electors proportionnally to each candidate. The New Hampshire attributes its 4 great electors by electoral county.
How to win ?
To win, a candidate must get 270 Great Electors. In a case of equality (269 each), the House of Representatives will elect the president and the senate will elect the vice-president.
