Barack Obama faces additional pressure and scrutiny tonight in the highly anticipated rematch with Mitt Romney after the U.S. president's widely criticized first debate performance dispirited Democrats and sparked a surge in support for the former Massachusetts governor.

The two presidential candidates square off in New York in a town hall-style debate — the second of three debates  — where they will field questions from undecided voters on a range of issues. But the focus will be on the president and whether he can reverse the momentum gained by his challenger.

"Everybody is putting the pressure on this debate for him to turn the tide, and I just think that's a really huge task and a huge expectation for a town hall debate," political strategist Brett O’Donnell, who helped prepare Romney for his crucial Florida primary debates, told CBC News.

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"The poor performance from the first debate was so magnified that they've now said we have to have a great debate in the second debate to turn the campaign around. Well that's placed a premium on the debate as opposed to other parts of the campaign, and I think it's very difficult to turn an entire campaign based on an hour and a half town hall debate."

Obama, who was criticized for being listless in the last encounter, has conceded that he "had a bad night," but a better performance is expected for tonight's political sparring match. His campaign says he has hunkered down and spent more time preparing. Campaign officials suggest that the president will take a more aggressive stance, possibly a watered-down version of Vice-President Joe Biden's style in his matchup against congressman Paul Ryan last week.

Obama will pointedly challenge Romney on specific policies, and may bring up perceived weaknesses that Obama ignored in their first contest, which could include Romney's tax returns, his time as head of Bain Capital, offshore accounts and his controversial "47 per cent" comments.

"It's pretty important for him to perform well," Alan Schroeder a professor in the School of Journalism at Northeastern University in Boston, and an expert on televised debates, told CBC News. "Going to be a lot of attention on him, likely to be a good-sized audience largely to see if he can do any better."

Remaining debates could be crucial

Charlie Cook, political analyst and editor and publisher of the newsletter the Cook Political Report, told CBC News that going into the first debate, internal polls showed that Obama was on the verge of putting the race away. But the debate seems to have changed those dynamics and given Romney a boost.

"We're looking at a real, real, real close race, and what happens in the second and third debates are going to matter," he said.

National polls now show Romney with a very slight edge, Cook said. But despite Obama's debate performance and Romney's surge, polls in some of the swing states, including the crucial state of Ohio, still give Obama the advantage, Cook said. But if Obama falters again, that could move those swing state polls in Romney's direction.

"You would see that resistance to Ohio, Colorado, Nevada would start wearing thin. I can't imagine that Obama's performance will be as bad as last time. But another weak performance by Obama could make the swing states look like the national numbers where Romney is up a bit," Cook said.

Town hall audience a factor

Although Obama is planning to go on the offensive, the debate format will require him to seek the right balance between being passionate and presidential.

"It's no secret that the Obama campaign realizes that the president has to go on offence and that he's got to be more aggressive," O’Donnell said. "The question is how aggressive he can be in a town hall meeting. He can't be overly aggressive with an audience sitting right there."

Schroeder agreed that it's a little more difficult to be "really bare-knuckled aggressive, because you have the audience there to get their questions answered. They're not there to watch a boxing match."

But Schroeder said there will be openings to attack if a question is asked that gives one of the candidates an opportunity to make a comparison between himself and his opponent.

Some observers have suggested that Romney's stiffness may give Obama a slight advantage in the town hall setting. But Schroeder said that neither has an "emotional style."

"I don't think either one of them is going to turn into Oprah Winfrey overnight, so I actually think they're kind of evenly matched. They don't have the Bill Clinton skills for this type of encounter."

As well, unlike Obama, Romney has had lots of practice in town hall settings taking questions from the audience.

University of California, San Diego political science professor Samuel Popkin said Obama has to be positive about what he's done and he has to offer a better narrative than Romney. Popkin, who helped prepare U.S. President Jimmy Carter in his debate against Republican candidate Ronald Reagan, said Obama doesn't necessarily have to be more aggressive, but just more assertive and positive.

"Every incumbent's secret line is the Roosevelt line: Don't change horses in the middle of the stream. But that means persuading people you're already at the middle and you're going to be able to make it across and you've got charge of the horse," Popkin told CBC News.

Popkin, who also authored The Candidate: What it Takes to Win — and Hold — the White House, added that it will be crucial for Obama to dispel  Romney's assertion that he can end political gridlock because, as governor of Massachusetts, he was able to work with Democrats.

"If people decide that is correct, Romney's the next president. It's that important, it's extremely important. [Romney saying]

'I can end gridlock because I am a solver who puts it all on the table and works with everybody.'

As for Romney, O'Donnell said his challenge will be in facing a more spirited opponent this time.

"He has to deal with an overly aggressive Obama and make sure he doesn't play more defence than offence. The audience introduces another element to the debate and he has to connect with that audience."

Romney's advantage in the last debate, Cook said, was that he did well at being himself — a pragmatic, non-ideological problem-solver who is right of centre but not too far right.

Cook's advice to Romney for this debate is simple: "Do exactly what you did. Don't do anything differently."