And as you may remember from high school civics, the presidential candidate who gets the most votes in each state gets that state's electoral votes which are allotted according to population. reports CBS News Chief Washington Correspondent Bob Schieffer.
(Check out CBS News.com's interactive electoral map.)
California with a population of 31 million has the most electoral votes: 54. Low population states like the Dakotas have only three. With 538 electoral votes at stake, a candidate needs 270 to win.
So it's possible, for example, that Democrat Al Gore could carry California and New York - two states where he's favored - and need only 14 additional states and the District of Columbia to win the presidency. If Republican George W. Bush carried the rest of the country, he'd no doubt win the popular vote, but lose the election.
That hasn't happened since 1888, when Democratic incumbent Grover Cleveland got more votes than Republican Benjamin Harrison, but lost the presidency as Harrison piled up a big lead in the Electoral College.
Then there's the real nightmare: When it's this close, an Electoral College tie is possible. That last happened with Thomas Jefferson and Aaron Burr in 1800. As it was then, a tie would mean the next president would be selected by the House of Representatives. In 1800, it took Congress 39 ballots to select Jefferson.
By the way, it would be the new Congress, the one elected Tuesday, that would pick the new president. How would it be done? Each state gets one vote and each state congressional delegation would decide how to cast it.
That presents interesting possibilities. For example, Bush should carry his home state of Texas in a landslide. But the Texas congressional delegation will probably have more Democrats than Republicans. Would they vote on party lines and cast the Texas vote for Gore? Several Texas Democrats have already said probably not, but it would be their choice.
And here's one that's often overlooked: In an electoral tie, who selects the vice president? Some might say, "Who cares?" But the answer is, the U.S. Senate does.