The winner of the US presidential election is not always the candidate who wins the popular vote - the path to victory is to win a majority in the electoral college.
Each state has a certain number of electors who elect the president - the number depends on the state's population - and the trick is to win enough states to stack up 270 electors' votes.
The map to the right shows how the states have voted since 1948.
Below we reprint five expert projections, based partly on the latest opinion polls, which indicate how the race could end in 2008.
Each website regularly updates its map. This is what the maps looked like at 1000 GMT on Monday 3 November.
CQ Politics: Obama 311/McCain 160
Real Clear Politics: Obama 278/McCain 132
Pollster.com: Obama 311/McCain 142
New York Times: Obama 291/McCain 163
Crystal Ball: Obama 364/McCain 174
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more, including maps and results of past elections:
http://news.bbc.co.uk/2/hi/americas/us_elections_2008/7693060.stmpoll tracker (4 polls):
http://news.bbc.co.uk/2/hi/in_depth/629/629/7360265.stm