The election of the President of the United States and the Vice President of the United States is indirect. Presidential electors are selected on a state by state basis as determined by the laws of each state. Currently each state uses the popular vote on Election Day to elect electors. Although ballots list the names of the presidential candidates, voters within the 50 states and the District of Columbia are actually choosing Electors from their state when they vote for President and Vice President. These Presidential Electors in turn cast the official (electoral) votes for those two offices. Although the nationwide popular vote is calculated by official and media organizations, it has no legal role in presidential elections.
 Apportionment of electors
The present allotment of electors by state is shown in the article List of U.S. states by population.
The size of the electoral college has been set at 538 since the election of 1964. Each state is allocated as many electors as it has Representatives and Senators in the United States Congress. Since the most populous states have the most seats in congress, they also have the most electors. The states with the most are California (55), followed by Texas (34) and New York (31). The smallest states by population, Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont, and Wyoming, have three electors each. Because the number of representatives for each state is determined decennially by the United States Census, the electoral votes for each state are also determined by the Census every ten years. The number of electors is equal to the total membership of both houses of Congress, plus additional electors allocated to the District of Columbia. There are currently 100 Senators and 435 Members of the House of Representatives, so the total membership of both houses of Congress is 535. An additional 3 electors are allocated to the District of Columbia, making the total number of electors equal to 538. A candidate must receive a majority of votes from the electoral college (currently 270) to win the Presidency, If no one receives a majority, the election is determined by Congress (the House for presidential candidates, the Senate for vice presidential candidates).
Under the 23rd Amendment, the District of Columbia is allocated as many Electors as it would have if it were a state, except that it cannot have more Electors than the least populous state. The least populous state (currently Wyoming) has 3 Electors, so the District cannot have more than 3 Electors. If the least populous state had 4 Electors, however, the District would be entitled to a maximum of 4 Electors. At its current population, however, it would remain at 3 because it is not nearly as large as any of the states that receive 4 Electors.
Presidential elector candidates are nominated by their state political parties in the summer before the Election Day. Each state provides its own means for the nomination of electors. In some states, such as Oklahoma, the Electors are nominated in primaries the same way that other candidates are nominated. Other states, such as Virginia and North Carolina, nominate electors in party conventions. In Pennsylvania, the campaign committees of the candidates name their candidates for Presidential Elector (an attempt to discourage faithless Electors). All states require the names of all Electors to be filed with the Secretary of State (or equivalent) at least a month prior to election day.
On election day, voters cast ballots for slates of Presidential Electors pledged to the candidates for president and vice president. In most states, the candidates that win the popular vote have their entire slate of Electors elected. At the time of the state canvass of the vote, the Secretary of State (or equivalent) signs a special form called the Certificate of Ascertainment which sets forth the people elected to the office of Presidential Elector, along with the number of votes cast for every party's slate of Elector nominees. These Certificates of Ascertainment are forwarded to the Office of the Vice President to be used to verify that the people who cast the electoral votes are in fact the people who were elected for that purpose.
Two states do not elect the Presidential Electors as a single slate. Maine and Nebraska elect two electors by a statewide ballot and choose their remaining Electors by congressional district. The method has been used in Maine since 1972 and Nebraska since 1991, though neither has split its electoral votes in modern elections.
 Electing the President and Vice President
The Presidential Electors meet in their respective state capitals in December, 41 days following the election, at which time they cast their electoral votes. Thus the "electoral college" never meets as one national body. They ballot for President, then ballot for vice president. The Elector is not allowed to vote for a Presidential candidate and a Vice-Presidential candidate who are both from the same state as the Elector. Afterward, the Electors sign a document called the Certificate of Vote which sets forth the number of votes cast for these two offices and is signed by all Electors. Multiple copies of the Certificate of Vote are signed, in order to provide multiple originals in case one is lost. One copy is sent to president of the Senate (i.e. the sitting Vice President of the United States); the certificates are placed in two special mahogany boxes where they await a joint session of the new Congress where they are opened and counted. Candidates must receive a majority of the electoral vote to be declared the president-elect or vice-president-elect.
If no candidate for President receives an absolute electoral majority 270 votes out of the 538 possible, then the new House of Representatives is required to go into session immediately to vote for President. (This would likely just occur when more than two candidates receive electoral votes, but could theoretically happen in a two-person contest, if each received exactly 269 electoral votes). In this case, the House of Representatives chooses from the three candidates who received the most electoral votes, but could not establish a majority of votes in the College. The House votes en-bloc by state for this purpose (that is, one vote per state, which is determined by the majority decision of the delegation from that state; if a state delegation is evenly split, a deadlock normally results, and that state is considered as abstaining). This vote would be repeated if necessary until one candidate receives the votes of more than half the state delegations—at least 26 state votes, given the current number, 50, of states in the union.
If no candidate for Vice President receives an absolute majority of electoral votes, then the United States Senate must do the same, with the top two vote getters for that office as candidates. The Senate votes in the normal manner in this case, not by States. It is unclear if the sitting Vice President would be entitled to cast his usual tie-breaking vote if the Senate should be evenly split on the matter.
If the House of Representatives has not chosen a winner in time for the inauguration (noon on January 20), then the Constitution of the United States specifies that the new Vice President becomes Acting President until the House selects a President. If the winner of the Vice Presidential election is not known by then either, then under the Presidential Succession Act of 1947, the Speaker of the House of Representatives would become Acting President until the House selects a President or the Senate selects a Vice President.
On the one hand, the Twelfth Amendment specifies that the Senate should choose the Vice President, and it does not admit of a time limit on the selection process. On the other hand, the Twenty-Fifth Amendment allows the President to nominate a Vice President if a vacancy should occur.
As of 2006, the House of Representatives has elected the President on two occasions, in 1801 and in 1825. The Senate has chosen the Vice President once, in 1837.
The Electoral College dilutes the votes of population centers that might have different concerns from the rest of the country. The system is supposed to require presidential candidates to appeal to many different types of interests, rather than, say, the urban or rural voter only. The College enabled the Founding Fathers to deftly incorporate the Connecticut Compromise and three-fifths compromise into the system of choosing the President and Vice President, sparing the convention further acrimony over the issue of state representation.
In the Federalist Papers No. 39, James Madison argued that the Constitution was designed to be a mixture of federal (state-based) and national (population-based) government. The Congress would have two houses, one federal and one national in character, while the President would be elected by a mixture of the two modes, giving some electoral power to the states and some to the people in general. Both the Congress and the President would be elected by mixed federal and national means. 
In the elections of 1824, 1876, 1888, and 2000, the candidate who received a plurality of the popular vote did not become president. The 1824 election was eventually decided by Congress and thus distinct from the last three which were decided without.
Proponents of the system counter that the Electoral College requires candidates to garner more widespread support throughout the Union; a popular vote system could elect a person who wins by a large margin in a few states over another person who wins by small margins in most states. The latter candidate, the argument goes, has to appeal to a broader array of interests than the former and is less likely to be a demagogue or extremist. However, the Electoral College is not guaranteed to favor the latter candidate in that scenario. In fact, given the 2000 allocation of electors, a candidate could win with the support of just the 11 largest states.
Further, there is currently no such thing as a national "popular vote," because combining the different statewide popular votes into a single national vote has no legal or statistical significance, and claims of the electoral college denying the "popular will" are debatable. For example, voters in Massachusetts or Texas in 2004, as their respective states were sure to vote Democrat or Republican for President, were more likely to vote for a third party candidate, or not vote at all, since their vote for their preferred Democrat or Republican candidate was extremely unlikely to change the result. Conversely, a voter in Florida was more likely to vote Democrat or Republican, even if they favored a third-party candidate, because their vote was much more likely to make a difference.
The effects of this phenomenon are somewhat known, but impossible to quantify in any close election, such as in 2000, when Al Gore had merely 0.5% more of the cast votes than George W. Bush.
 Focus on large swing states
Most states use a winner-take-all system, in which the candidate with the most votes in that state receives all of the state's electoral votes. Candidates will pay more attention to larger states without a clear favorite. California, Texas, and New York, in spite of having the largest populations, are usually considered safe for a particular party, and will therefore be ignored by candidates (except for fundraising efforts).
It is also theoretically possible to win the election by winning all of eleven states and disregarding the rest of the country. If one ticket were to take Texas (34 votes), Pennsylvania (21), Ohio (20), North Carolina (15), New York (31), New Jersey (15), Michigan (17), Illinois (21), Georgia (15), Florida (27) and California (55), that ticket would have 271 votes, which would be enough to win. (In theory, if a minimum number of voters were to vote in those eleven states, the other major ticket could have a landslide victory in the popular vote and still lose the election.)
Proponents claim, however, that adoption of the popular vote would simply shift the disproportionate focus to large cities at the expense of rural areas. 
 Disadvantage for third parties
Some proponents of proportional representation claim that, because third parties generally start as regional phenomena  and because the Electoral College is a form of regional allocation, the Electoral College would enhance the power of third parties if electoral votes were allocated by proportional representation. 
 Arguments for and against the current system
 Unrepresented Territories
If an American national is a resident of one of the unincorporated territories of the United States (i.e., American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands), he or she cannot vote for electors for President.
 Requires a distribution of popular support to win the Presidency
Proponents of the Electoral College argue that organizing votes by regions forces a candidate to seek popular support over a majority of the country. Since a candidate cannot count on winning the election based solely on a heavy concentration of votes in a few areas, the Electoral College avoids much of the sectionalism that has plagued other geographically large nations, such as China, India, the Soviet Union, and the Roman Empire. Electoral College opponents, however, argue that this regional system can dilute the overall will of the people in close elections by thwarting the candidate with the popular majority. Considering the distrust the Constitution's framers had of direct democracy, this result can be viewed as a foreseeable and desirable result of the arrangement.
Also, there are many examples of candidates winning the Electoral College despite a lack of broad national support. Lincoln won in 1860 without taking a single southern state. The same thing occurred again with the Republican candidates in 1880 and 1888, and nearly happened (save border states West Virginia and Kentucky) in 1896, 1900, 1904, and 1908, and 1924.
 Maintains the federal character of the nation
The United States of America is a federal coalition; it consists of component states, each of which are joined in an alliance with what has, traditionally, been a small, state-controlled central government. Proponents of the current system argue that the "collective opinion" of even a small state merits attention not to be entirely overshadowed simply by a small portion of a very populous state. For many years early in the nation's history, up until the Jacksonian Era, most states appointed their electors by a vote of the state legislature, and proponents argue that, in the end, the election of the President must still come down to the decisions of each state, or the federal nature of the United States will give way to a single massive, centralized government.