Democrat Barack Obama is building solid leads in battlegrounds Florida, Ohio and Pennsylvania, according to new polls released on Wednesday in a trio of states that could be the key to victory on 4 November.

The surveys reveal new momentum for the Illinois senator against Republican John McCain, as the rivals dash back to Washington to vote on a US$700-billion Wall Street bailout package.

The Quinnipiac University poll suggests Obama won Friday's presidential debate and that McCain's vice presidential running mate Sarah Palin is suffering from sliding popularity, after a stunning initial impact on the race.

They also find that voters trust Obama more to handle the financial crisis rocking the US economy and he seems to be convincing Americans he is ready to be president.

"It is difficult to find a modern competitive presidential race that has swung so dramatically, so quickly and so sharply this late in the campaign," said Peter Brown, assistant director of the Quinnipiac polling institute.

Obama is leading

The surveys show that in Pennsylvania, Obama leads McCain by a gaping 54 percent to 39 percent after the debate, compared to 49 percent to 43 percent before the debate.

He is up 51 percent to 43 percent in swing state Florida; compared to a 49 to 43 percent lead before Friday's first of three high-stakes presidential debates.

And in Ohio, Obama is up eight points, 50 percent to 42 percent, after having led by 49 percent to 42 percent before the clash in Mississippi.

The trio of swing states ? which have a history of going either Republican or Democrat and swinging presidential elections ? are vital stepping stones to the White House.

No candidate has won the presidency since 1960 without securing two of the three battlegrounds, all of which are seeing pitched duels and repeated campaign visits between Obama and McCain five weeks from election day.

Obama won the debate

Crucially for the Illinois senator, 15 to 27 percent of prized independent voters in each state said he had won the debate against McCain.

"Senator John McCain has his work cut out for him if he is to win the presidency and there does not appear to be a role model for such a comeback in the last half century," Brown said.

"Senator Obama clearly won the debate, voters say. Their opinion of Governor Sarah Palin has gone south and the Wall Street meltdown has been a dagger to McCain's political heart," he said.

The polls among likely voters in the three states were conducted in two groups, between 22 and 26 September and between 27 and 29 September. The maximum margin of error was 3.4 percent.

McCain, Obama and Democratic vice presidential pick Senator Joseph Biden are all due for an intriguing close encounter in the Senate when the vote on the bailout, originally rejected by the House of Representatives goes ahead late Wednesday.

On Tuesday, Obama noted the bill's failure had triggered a bloodbath on world markets, with US$1.2-trillion wiped off New York share values alone on Monday before a partial rebound on Tuesday.

'Millions of jobs could be lost'

It was an 'outrage' that taxpayers had to foot the bill for financiers' folly, Obama said, but stressed that without action by Congress, "millions of jobs could be lost, and a long and painful recession could follow."

McCain said on Tuesday in Des Moines, Iowa: "Yesterday the country and the world looked to Washington for leadership and Congress once again came up empty-handed.

"I am disappointed at the lack of resolve and bipartisan goodwill among members of both parties to fix this problem," the Arizona senator said.

"Congressional inaction has put every American and the entire economy at the gravest risk," McCain warned, citing individual companies and student groups now struggling to get loans because of the credit crunch.

Both Obama and McCain have said they will vote for the bill, which would allow the government to buy up to US$700-billion in bad, mortgage-related debts from financial firms endangered by the collapse of the US housing market.

Backers hope a successful Senate vote will prod the House to come on board, with both McCain and Obama stepping up their appeals to party colleagues to put the risk of economic disaster ahead of their own misgivings about the bill.