On November 2, Americans will go to the polls to choose their next president. While millions of people will cast their votes, the magic number for victory is only 270.

Who should choose the president, the people or Congress? That was the question facing the framers of the U.S. Constitution more than two centuries ago.

"The Founding Fathers weren't sure that they could trust the American people to cast a vote for president, so they set up the Electoral College system," said Candice Nelson, professor of government at American University.

The Electoral College was a compromise between those who wanted the people to elect the president directly, and those who wanted Congress to choose the nation's leader.

It creates a two-step process for electing the president. On Election Day, voters cast their ballots for the presidential candidate of their choice. In most states, the candidate who wins the popular vote gets all of the state's electoral votes.

There are a total of 538 votes in the Electoral College, with each state getting the same number of votes as it has representatives in the two houses of Congress.

For instance, a large state like California has 55 electoral votes, while Rhode Island, a much smaller state, has only four. The District of Columbia, which has no voting members in Congress, has three Electoral votes.

"You've got to have a majority 270 votes in the Electoral College to win, and you accumulate them state-by-state, with large states like California having the lions-share of the Electoral College vote," explains presidential historian Allan Lichtman.

The advantages and disadvantages of the Electoral College have been debated for years. Norm Ornstein, a political scholar at the American Enterprise Institute, says that, in this system, votes from smaller states count just as much as those in larger states.

"If we didn't have an Electoral College, what reason would candidates ever have to campaign in the middle of the country? Why would you ever want to go to the Rocky Mountain region of the United States where there are no votes?" he said.

But the system is not without its critics. As we learned in the 2000 presidential election, a candidate who loses the popular vote can still become president. But George W. Bush wasn't the first. Three other presidents over the past two centuries also reached the nation's top job, without winning the popular vote.

Despite the controversy four years ago, political analyst Stephen Hess of the Brookings Institution believes the Electoral College is here to stay.

"Well, the strange part about it is, if it were going to go, it would have gone then, because there were an awful lot of people that said, 'hey, this doesn't work very well.' And that didn't happen," said Mr. Hess.

As the presidential campaign enters its final days, the candidates will be waging a state-by-state battle for every vote, with their eye on the ultimate prize, the 270 electoral votes needed to win the presidency.