Upping the pace as next Tuesday's election loomed, Mr Obama was also due to hold his first joint rally with former president Bill Clinton at a midnight event in Orlando, Florida.

The 47-year-old Illinois senator, bidding to be America's first black president, is riding high in the polls while Republican rival John McCain is beset by reports of internal disarray between his aides and running mate Sarah Palin.

In Virginia late on Tuesday, Mr Obama said history was in the air as he built a double-digit poll lead in a state that last voted for a Democratic White House hopeful in 1964.

Campaigning in the picturesque Shenandoah Valley, Obama said the last Democratic presidential contender to come to the region was the racist Stephen Douglas - Abraham Lincoln's opponent before the 1861-1865 Civil War.

'That's a long distance to travel,' he said, stressing in a now-daily warning against complacency: 'Don't think for one minute that power will concede without a fight.

'We're going to have to work like our future depends on it, because it does,' he said.

Mr McCain, 72, was on Wednesday also campaigning in the Sunshine State, a pivotal battleground that decided the 2000 election in favor of President George W. Bush after a recount fiasco that went all the way to the Supreme Court.

An estimated two million Floridians have voted early and queues have grown so lengthy that Governor Charlie Crist - a moderate Republican who is reportedly critical of Mr McCain's campaign - has extended balloting hours.

Florida had appeared a certain win for Mr McCain not many weeks ago, but a Los Angeles Times poll late on Tuesday had Mr Obama ahead by 50-43 per cent. It also had Mr Obama on 49 per cent to Mr McCain's 40 in Ohio, another major toss-up state.

The newspaper said that in both states, Mr Obama 'has opened commanding leads over McCain among women, young people, first-time voters and blacks and other minorities.'

Mr McCain is portraying Mr Obama as an ultra-liberal politician plotting to raise taxes across the board.

'Senator Obama is running to be redistributionist-in-chief, I'm running to be commander-in-chief,' he said.

That message did not appear to be resonating with voters. A new ABC News-Washington Post poll said Mr Obama was the first Democratic hopeful since Mr Clinton to lead his Republican rival on taxes, by 10 points.

Overall, the Democrat led Mr McCain by 52-45 per cent in the poll.

Mr Obama's 30-minute, prime-time television pitch was being taken out at a cost estimated by media analysts at up to five million US dollars (S$7.5 million) on three of the four national networks: CBS, NBC and Fox.

Virtually guaranteeing a huge audience, the 'infomercial' was to directly precede the start of the latest and potentially decisive game of baseball's World Series between the Philadelphia Phillies and Florida's Tampa Bay Rays.

Aides were tight-lipped about the content but the broadcast was likely to emulate the slickly produced biographical video shown at the Democratic convention in late August with Obama offering his 'closing argument' to voters.

The Chicagoan was heading to Florida after a rally earlier on Wednesday in North Carolina, which like Virginia is threatening to turn Democratic blue for the first time in decades.

Mr Clinton meanwhile could help Obama seal the deal with the kind of white, working-class voters who backed the former president's wife Hillary in the Democratic nominating slugfest earlier in the year.

Bill Clinton, who has been unhappy over his wife's defeat, was heading to Florida from the rust-belt state of Pennsylvania, where more than 9,000 supporters turned out at an Obama rally on Tuesday despite poor weather.

Further west, a Suffolk University poll showed Mr Obama surging to a lead of 50 percent-40 per cent over Mr McCain in Nevada, which along with Colorado and New Mexico offer the Democrat another route to the White House if his strategy in states east like Florida and Ohio fails to come off.

The McCain campaign was also expected on Wednesday to continue to put on a public display of unity after reports of infighting between the Arizona senator and his vice presidential pick Sarah Palin.

Allies of Mrs Palin have given interviews anonymously to the press recently complaining about her handling by the Mr McCain team, while Mr McCain's senior aides have hit back, branding Mrs Palin a 'diva' and a 'whack job'. -- AFP