( L - R ) Obama, Mccain

WASHINGTON (AP):

Barack Obama drew massive crowds to some of his final campaign rallies as Americans appeared likely to cap the longest, most expensive White House campaign ever by electing the Democrat as the first black United States president on Tuesday.

Republican John McCain, looking to score the United States' biggest political upset in 60 years, assured supporters Sunday that the race is tightening.

"I've been in a lot of campaigns. I know the momentum is there," McCain said at a rally in Pennsylvania, traditionally a Democratic-leaning state that he must wrest from Obama.

Obama leading

But polls show Obama leading in Pennsylvania and other key states. Nationally, several major polls show Obama with a seven to eight percentage-point advantage.

A victory would mark a stunning rise for the 47-year-old Obama, who was little known nationally before being elected as a senator from Illinois four years ago. He began running for president just two years later.

Obama exuded confidence Sunday. "The crowds seem to grow and everybody's got a smile on their face. You start thinking that maybe we might be able to win an election on November 4."

The electoral map clearly favours Obama. To be elected, a candidate must win at least 270 of the 538 electoral votes distributed to states roughly in proportion to their population. In most cases, the candidate who wins a plurality of votes in a state wins all of that state's electoral votes.

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