White House candidate Barack Obama on Monday accused John McCain of launching an "ugly" bid to stave off defeat as he blitzed the crucial swing state of Florida with onetime foe Hillary Clinton.

With tension boiling in the White House race just 15 days before the election, Obama implored supporters to flood early voting stations which opened on Monday in a state which broke Democratic hearts in 2000 and 2004.

But Republican McCain raised questions about Obama's capacity to lead, ironically echoing attack lines the former first lady used against the Illinois senator during their ill-tempered primary duel earlier this year.

Obama accused McCain of stooping to cynical "small" politics in a desperate attempt to stage an 11th-hour rescue for his faltering presidential hopes.

'Do-anything politics'

"In the final days of campaigns, the say-anything, do-anything politics too often takes over," Obama told 8000 supporters in a rally in Tampa, before traveling on to stump with Clinton for the first time since June in Orlando.

"We've seen it before and we're seeing it again — ugly phone calls, misleading mail, misleading TV ads, careless, outrageous comments," Obama said.

"It's getting so bad that even Senator McCain's running mate denounced his tactics last night.... You really have to work hard to violate Governor Palin's standards on negative campaigning."

Sarah Palin, who has launched some of the most stinging attacks against Obama, said on Sunday that if she were in charge, she would not rely on "the old conventional ways of campaigning, that includes those robo-calls."

The McCain campaign has been using automated calls to question Obama's character and values in a bid to drive up his negative ratings in swing states.

Obama, however, was basking on Monday in his high-power endorsement by former Republican secretary of state Colin Powell and the news that he raked in a staggering $150-million in fundraising in September.

The Democrat leads national polls and appears to be in a position to squeeze McCain across the electoral map, with time running out for the Republican to launch a comeback.

'Nothing is inevitable'

But McCain, following Obama's weekend footsteps to the midwestern battleground state of Missouri, warned "nothing is inevitable" despite his huge cash deficit and polls which give Obama the lead two weeks out.

"We never give up, we never quit," the Arizona senator told cheering supporters and accused Obama of wanting to "redistribute wealth".

McCain warned voters that Obama "won't have the right response" to crises which emerge on the world stage and is planning to "raise taxes, increase spending, and concede defeat in Iraq".

"The next president won't have time to get used to the office. We face many challenges here at home, and many enemies abroad in this dangerous world," McCain told a rally in Belton, Missouri.

"What America needs in this hour is a fighter; someone who puts all his cards on the table and trusts the judgment of the American people."

But Clinton, appearing at a rally with Obama on a balmy evening in Florida, said McCain just represented a prolongation of the presidency of George W. Bush.

"We are in an economic crisis born and bred by the failed Republican policies of George Bush and John McCain.

"George Bush has practiced what John McCain has preached."

The latest daily tracking poll of registered voters by Gallup showed Obama expanding his lead to 11 points and the Democrat was up nine points in the likely voters category, perhaps reflecting Powell's impact on the race.

The daily Rasmussen survey however, had McCain narrowing the race to four points, trailing Obama by 50 percent to 46 percent of voters nationwide.

A Suffolk University poll meanwhile found Obama leading by 51 to 42 percent in another bellwether state, Ohio, and McCain was up by a single point in Missouri, a traditional Republican state threatening to go Democratic.

The Democratic nominee will spend much of the week charging through Republican territory, including Florida, Virginia and Iowa, hoping to convert his lead on the electoral map into a thumping victory.

AFP