Instead, in a peculiar quirk of the U.S. political system, they will choose a slate of state officials or party leaders known as electors, either Democrat or Republican, who will make up the Electoral College.

These 538 representatives will then meet in their state capitals on Dec. 15 to elect the next occupant of the White House, based on whether Democrat Barack Obama or Republican John McCain won the most votes in their states.

"To be honest I think a lot of Americans don't really understand it either," said Chris Dreibelbis, communications director at the Reform Institute, asked to explain the complex, unique American system which dates back to the 1800s.

Each of the 50 U.S. states, plus the nation's capital Washington DC, has a minimum of three Electoral College votes, but those with the largest populations have the most.

To win the Nov. 4 election, either candidate has to win 270 Electoral College votes or more. California is the largest state with 55 Electoral College votes, followed by Texas with 34.

The candidate who wins the popular vote in the state wins all its Electoral College votes, except in Maine and Nebraska, which use a tiered system.

That's why swing states such as Ohio with 20 Electoral College votes, or Pennsylvania with 21 can prove such rich pickings for candidates needing to bump up their tallies.

It's also why a candidate can win the popular vote, but lose the White House, as happened in 2000 when Democrat Al Gore lost in Florida, and its then 25 Electoral College votes tipped Republican George W. Bush to victory.

Nationally Gore had won the most popular votes taking some 50,996,582 compared with Bush on 50,456,062, but with Florida in his pocket Bush got 271 Electoral votes compared to 266 for Gore.

The Electoral College was established by the founding fathers and has been around in some form since the early 1800s when vast distances and a lack of communications meant organizing and counting a national popular vote posed immense hurdles.

"I think it was felt that creating this Electoral College would simplify the process and ensure that there was indeed a clear winner," said Dreibelbis.

Critics say the Electoral College is not always reflective of the national will, and allows candidates to focus on a handful of key swing states instead of running a truly national campaign.

Supporters however argue that changing the system to a direct vote for the president would concentrate too much power in the hands of urban populations to the detriment of rural, more sparsely populated states.

Over the past two centuries, hundreds of motions have been brought before U.S. lawmakers to either reform or abolish the Electoral College. But none has attracted enough support.

"Honestly, I have to say from my perspective there has been largely ambivalence towards it. Here in Washington I'm not seeing any big calls for abolishing the Electoral College," said Dreibelbis.

"Who knows? That may change after this election, if you have a situation where one candidate gets the majority of the popular vote and another wins the Electoral College. We had that in 2000. So if that becomes a trend I probably would say there would be a growing chorus to revisit the Electoral College."

In the event of the tie, where each candidate won 269 electoral votes, then the House of Representatives would be called on to choose the president, with lawmakers voting by state delegations.

But there is one situation where the rules remain unclear, and which has never been tested. What would happen if the winner of the Nov. 4 election were to die before the Electoral College meets in mid-December to make its choice?

Once the Electoral College meets, if anything were to happen to the president-elect before the January inauguration, then the vice president elect would step into his shoes.