( L - R ) McCain, Obama

WASHINGTON, D.C. (AP):

Democrat Barack Obama, sensing victory in his reach, urged supporters to keep up the fight yesterday in the final hours of his historic quest to become the first black United States (US) president. Republican John McCain pushed for a last-minute upset.

On the last full day of his 21-month campaign for the White House, Obama told supporters in Jacksonville, Florida, that he could win what has proven to be the longest, most expensive US presidential contest in history - but only with their support.

"That's how we're gonna change this country - with your help," he told the crowd, amid chants of "O-bam-a! O-bam-a!"

McCain meanwhile was racing through seven states in a last campaign swing that ends this morning, in a bid to persuade undecided voters that he, not his rival, was more qualified to lead the world's most powerful nation.

"I need your vote," an arm-pumping McCain told supporters yesterday in Tennessee. "We need real change to Washington and we have to fight for it. And we will fight for it with your help ... They may not know it, but the Mac is back. We're gonna win this election."

While Republican experts argued the race was tightening, several polls suggested Obama's lead was widening, with Obama leading in Pennsylvania and other states McCain must win to have a chance of capturing the presidency.

A USA Today/Gallup poll published yesterday found likely voters nationwide favouring Obama by 11 points over McCain, 53-42 per cent, with a margin of error of two per cent. Other polls showed Obama with a seven or eight percentage point lead.

Polls conducted by Quinnipiac University suggested Obama was poised to win two critical swing states, Ohio and Pennsylvania, and was tied with McCain in a third, Florida. A win for Obama in any of these three states would be hard for McCain to overcome.

The poll released yesterday showed Obama leading in Ohio, 50-43, with a margin of error of 2.5 per cent. In Pennsylvania, the poll put Obama ahead by 52-42.

In Florida, the poll suggested the two candidates were in a statistical dead heat - Obama led McCain by 47-45, with a margin of error of 2.3 percentage points.

To win the presidency, 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.

The possibility of a dual defeat - in the White House and Congress - is likely not lost on Presiden George W Bush, who has maintained a low profile in the race.

White House spokeswoman Dana Perino said the incumbent's invisibility was by design - because "the Republican Party wanted to make this election about John McCain".

Determined to make sure that partisans translate their support into votes, both campaigns were focusing on Monday on get-out-the-vote efforts.

But a large part of the electorate has already rendered its verdict.

A record 27 million voters cast absentee or early ballots in 30 states as of Saturday night. Democrats outnumbered Republicans in pre-Election Day voting in key states.