The President of the United States is not elected directly by the people, but by what has come to be known as the Electoral College. The Electoral College consists of 538 electors*, who are chosen in the states on election day in November by the voters**. Each state has a number of electors equal to its total number of Senators (always two, of course) plus Representatives (at least one). Thus, each state has a number of electors which is more or less proportional to its population, except that the states with very small populations may have a disproportionately large number of electors, since they have at least three.
The Constitution specifies that each elector votes for one candidate for President and one for Vice-President, and that at least one of the two must be from a state different from that of the elector. In order to be elected, a candidate must receive an absolute majority of the votes in the electoral college, i.e., at least 538/2 = 269 + 1 = 270. (The Constitution provides a mechanism for choosing a President in case no candidate obtains a majority in the Electoral College, but it will be ignored here.)
The Constitution provides that each state should determine by legislation how to designate its electors. In forty-eight of the fifty states, a "winner-take-all" method of attributing electoral votes is used, in which the candidate who receives the most votes in the general election in a state (even if s/he does not receive a majority) receives all the electoral votes for the state. It will be observed that this has a very strong tendency to eliminate third party candidates from any consideration in the Electoral College, since they are unlikely to receive the largest number of votes in any state, and also that it reinforces the role of the states as entities, since each state votes as a single block in the Electoral College. (The two states which do not apply the "winner-take-all" method are Maine and Nebraska; they attribute electorals votes roughly in proportion to the number of votes obtained in the general election, but they represent a total of nine electoral votes, so their combined effect on the election outcome is very small.)
There has been a movement recently to adapt the functioning of the Electoral College to contemporary beliefs about the role of the people at large in a democracy. A significant proposal, which has been debated in a number of states, is that each state should adopt legislation such that its electoral vote would be attributed to the candidate who wins the largest number of popular votes in the nation, even if that candidate were not the winner in this or that state. If it were adopted by all the states, this proposal would guarantee that the President would be democratically elected (i.e., would be the choice of the majority of the voters in the US) without the need to amend the Constitution. Most recently, this idea was passed by the state legislature of California, but was vetoed by Governor Arnold Schwarzenegger, who maintained that it is incompatible with traditional American conceptions of federalism and the role of the states.
-=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=-
The Federal Election Commission's site has information about the Electoral College here.
Some technical legal considerations about the designation of electors and other topics can be found at the Cornell University Law School's website here. For more about the results of the 2004 election and the consequences of the structure of the electoral collge, see this site at the University of Michigan. The US National Atlas site has an article here about the Electoral College.
(One of the ways in which the doctrines of federalism are present in the federal government is that only states are represented in Congress, whether in the House or the Senate. Since the number of electors in the Electoral College is equal to the number of Senators plus the number of Representatives, this leads to the interesting paradox that the inhabitants of Washington, D.C., who are not represented in Congress, since the District of Columbia is not a state, could not vote in Presidential elections until 1961, with the adoption of the Twenty-third Amendment to the Constitution, which attributes three electoral votes to the District of Columbia.)
__________
* By a sort of transposition of terms from the French political system, it is common in French to use the expression "grands électeurs" to refer to the members of the Electoral College. In English, however, they are not called "big/large/tall/grand/great/super-sized electors", but simply "electors". [back to text].
** The individual citizens who vote are called "voters", not "electors". [back to text].