COLORADO - DEMOCRAT Barack Obama promised a 'new politics for a new time' and said he had a 'righteous wind' at his back as he basked in hefty poll leads just three days before Tuesday's historic election.

But Mr Obama's Republican White House rival John McCain attacked Mr Obama's patriotism after the Democrat said his momentous campaign had 'vindicated' his faith in the American people.

Meanwhile, after a mildly embarrassing revelation, Mr Obama's campaign returned a financial donation from a Kenyan aunt who lives in Boston after questions were raised over her immigration status.

The rivals blitzed key battleground states on Saturday, in what has been Republican territory in recent elections, reflecting Obama's edge in most swing states and in national polls as the race careens to a close.

'Don?t believe for a second that this election is over,' Mr Obama told 15,000 people in the balmy heat of the western battleground state of Nevada as his bid to become America's first black president reaches its climax.

'But I know this, Nevada, the time for change has come. We have a righteous wind at our back,' he said.

The Illinois senator, 47, once again tried to shackle Mr McCain to President George W. Bush's legacy and warned his rival would resort to 'slash and burn' tactics in the final hours.

But he said that the politics of division would not pull America out of its current financial crisis. 'We can steer ourselves out of this crisis - with a new politics for a new time.'

Mr McCain, seeking to make Tuesday's election a referendum on whether his rival was fit to lead in a perilous age, raised sharp questions about Mr Obama's readiness to be commander-in-chief.

Mr Obama had shown some 'impressive qualities,' Mr McCain, 72, said at a rally in Newport News, Virginia, but he argued his foe was the wrong choice for a dangerous world where 'millions of lives' were at stake.

He also slammed Mr Obama for a remark that has been part of the Chicago senator's campaign speeches for several months.

'(Obama) said the other day that his primary victory ?vindicated? his faith in America. My country has never had to prove anything to me, my friends. I?ve always had faith in it and I?ve been humbled and honoured to serve it.'

The attack was dismissed as 'pathetic' by an Obama campaign spokesman.

'It's pathetic that Mr John McCain would take a statement Barack Obama has been making for a year about his faith in the American people and distort it to attack his patriotism,' spokesman Bill Burton said.

?Sadly, this is what we?ve come to expect from a desperate, dishonourable campaign that will say anything in a failed attempt to win this election.?

Latest daily tracking surveys suggested that Mr Obama was in pole position heading into election day.

Rasmussen had the national race at 51 to 46 per cent in favour of the Democrat. Mr Gallup had Mr Obama gaining momentum and leading 52 per cent to 42 per cent in two polls designed to reflect different scenarios of likely voters.

Mr Obama headed from Nevada to Colorado, another Republican state in 2004 which polls show trending in his direction, before an evening rally in the midwestern bellwether of Missouri.

He and wife Michelle were then set to campaign in Ohio Sunday for three events including a rally with rocker Bruce Springsteen in Cleveland. Obama's running mate Joseph Biden was stumping in Indiana and Ohio on Saturday.

Mr McCain hit the trail in Virginia and headed to Pennsylvania later Saturday before traveling to New York to make a cameo appearance in television comedy show Saturday Night Live.

His running mate Mrs Sarah Palin, a heroine to conservative voters, held a rally in Florida and later the Alaska governor was heading to Virginia.

Aides said Mr Obama had not been in touch with his late father's sister, Ms Zeituni Onyango, 56, for at least four years, and questioned reporting about her residency status so close to the election.

Mr Obama spokesman Ben LaBolt said the campaign was returning US$265 (S$392) donated by the aunt to her nephew?s White House bid.

Foreigners cannot donate money to US presidential candidates. But aides refused to say whether returning the money was an acknowledgement that the aunt was an illegal alien.

The campaign ascribed ulterior motives to the revelations after wires agencies reported that Onyango had remained living in Boston despite having her request for asylum rejected by an immigration judge four years ago.

Senior McCain campaign aide Mark Salter declined to comment on the story.

'It's a family matter,' he said. -- AFP