Obama and Romney prepare for New York debate
Barack Obama and Mitt Romney are hunkered down with advisers ahead of Tuesday's debate in New York, with the US president under pressure to bounce back after a languid first performance.
Mr Obama is at a debate camp in Virginia, while Mr Romney is preparing in his home state of Massachusetts.
Meanwhile, the Romney campaign raised a record $170m (£106m) in September.
A new national opinion poll shows the rivals in a statistical dead heat, 21 days before the election.
The ABC News/Washington Post survey released on Monday suggested voters were 49% for the Democratic president and 46% in favour of his Republican rival - a lead within the survey's margin of error.
'Come out swinging'
Postal and early in-person voting is already under way in 43 of 50 US states, including some that could decide the election.
First Lady Michelle Obama said at a campaign event on Monday in the key swing state of Ohio that she had put her early ballot in the post on Monday.
Ahead of Tuesday's debate at Hofstra University in Hempstead, New York, Mr Obama has been preparing with a three-day debate camp at a golf resort in Williamsburg, Virginia.
On Sunday, during a break to meet volunteers at a local campaign office, he said: "It's going great."
Mr Obama's aides and the president himself have acknowledged he did not do well at the first encounter in Denver, Colorado.
Obama adviser Robert Gibbs told CNN on Sunday: "I think you'll see somebody [on Tuesday] who is very passionate about the choice that our country faces."
As former Massachusetts Governor Romney's advisers put him through his paces in that state, his team said September was its best month of campaign fundraising yet, bringing in $170m.
Their total was just shy of the $181m raised by the Obama campaign in the same period.
Earlier, Mr Romney's wife remarked on his rise in national opinion polls following his first clash with the president.
"That's what you call momentum," Ann Romney said in an interview with Philadelphia radio station WPHT.
Republican Senator Rob Portman, who has been preparing Mr Romney for the debates, told ABC News: "I think President Obama is going to come out swinging. He's going to have to compensate for a poor first debate."
Tuesday's 90-minute encounter, to be moderated by CNN chief political correspondent Candy Crowley, will follow a town hall format - different from the first encounter - and will feature questions from voters in the audience.
Experts say town hall-style debates demand more empathetic responses from the candidates and are less suited to the kind of direct attacks that are thought to have benefited Mr Romney in the last encounter.
Monday's ABC News/Washington Post poll found that enthusiasm among Romney supporters was up 11 percentage points in the last two weeks to 59%.
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But as US economic indicators continue to point to recovery, the survey also found that voters narrowly favoured the president rather than Mr Romney to nurture further growth.
Last week Mr Obama's deputy, Vice-President Joe Biden, assertively attacked Mr Romney as he debated with the Republican's running mate, Congressman Paul Ryan, in Kentucky.
The final presidential debate is scheduled for 22 October in Boca Raton, Florida.