BURLINGTON, Mass. (AP) — As Mitt Romney's campaign claimed new momentum in the race for the White House, President Barack Obama's political advisers on Sunday promised the incumbent would unleash his more aggressive side in Tuesday's debate to prevent their Republican rival from delivering another 'magical and theatrical performance.'

Obama and Romney hunkered down in private debate preparation for much of the day as aides offered a pre-debate sparring match on television.

They disagreed on much, but agreed that Romney bested Obama in their first meeting nearly two weeks ago — a performance that shifted the direction of a race that had favored the president but has since tightened in national and battleground state polls.

'He knows Mitt Romney had a better night at the first debate,' Obama spokeswoman Jennifer Psaki said of the president. 'The American people should expect to see a much more energized President Obama.'

Ed Gillespie, senior adviser to the Romney campaign, quipped that the former Massachusetts governor would be prepared regardless of Obama's adjustments: 'The president can change his style. He can change his tactics. He can't change his record.'

Obama spent the day with aides in swing state Virginia, while Romney stayed close to his Boston-area home ahead of Tuesday's prime-time, town hall-style debate at Hofstra University in Hempstead, N.Y., exactly three weeks before the Nov. 6 election.

Romney's advisers suggested the Republican nominee would continue to moderate his message — in tone, if not substance — as he did in the Oct. 3 meeting to help broaden his appeal to the narrow slice of undecided voters. In recent days, Romney has promised his tax plan would not benefit the wealthy, emphasized his work with Democrats as Massachusetts governor and downplayed plans to strengthen the nation's abortion laws.

He told an Iowa newspaper this week, for example, that he would not pursue abortion-related legislation if elected. That's in direct conflict with last year's pledge to the Susan B. Anthony List, an anti-abortion group, to cut federal funding from Planned Parenthood and support legislation to 'protect unborn children who are capable of feeling pain from abortion.'

'I think Mitt Romney's performance was, indeed, magical and theatrical,' Obama senior campaign adviser Robert Gibbs said of the first debate. 'Magical and theatrical largely because for 90 minutes he walked away from a campaign he had been running for more than six years previous to that.'

While the debates have proved critical, they are one element in larger campaigns that involve extensive ground games in virtually every state across the nation and a television ad war that may consume $1 billion before Election Day.

Through Monday, either absentee or in-person early voting has begun in 43 states.

Romney on Sunday released a new television spot showcasing footage from running mate Paul Ryan's first and only faceoff with Vice President Joe Biden last week. The ad features clips of Ryan saying the government 'can't keep spending money we don't have.'

The comments are juxtaposed with video from the debate of Biden laughing.

Ryan returned to his home state, Wisconsin, to help raise cash for Senate candidate Tommy Thompson. Wisconsin hasn't voted for a Republican for president since Ronald Reagan in 1984, but Ryan said recent victories, including the failed recall of Gov. Scott Walker, have it poised to deliver for both Romney and Thompson in just over three weeks.

'When we do that, we will look back at this moment as the day Wisconsin completed its journey,' Ryan said in Milwaukee. He planned to hold a public rally Monday morning in nearby Waukesha.

Obama aides said the president was clear-eyed about the need to have a better showing in his second debate with Romney. After a listless first performance, Obama was focused on delivering more pointed and aggressive responses.

He was ensconced in hours of debate practice Sunday at Kingsmill Resort, a luxury vacation spot in Williamsburg, Va. The president was shuttling between a house on the campus where he is staying and the resort's main building, where aides are set up for debate practice.

Obama took a brief afternoon break to visit volunteers at a campaign office in Williamsburg. After greeting volunteers and dropping off a few pizzas for lunch, he called campaign workers who couldn't be at the office Sunday to thank them for their efforts.

Asked by reporters about his debate preparation, Obama said, 'It is going great.'

The campaign picked the riverfront Virginia resort in part to get the president away from distractions at the White House. Some of Obama's official duties, including the attack in Libya that led to the death of four Americans, forced the president to cancel or cut short some of his prep sessions ahead of the first debate, and aides acknowledge he entered the first faceoff with less practice than they had wanted.

Virginia was also a political strategic pick for Obama. While he has no formal public events there, his mere presence in the competitive swing state is designed to drive local media coverage just over three weeks from Election Day.

Aides said Obama and his team were both studying up on policy and holding mock debates, featuring Sen. John Kerry, D-Mass., playing the role of Romney. Anita Dunn, a former Obama aide brought back to help with debate preparations, was playing the role of debate moderator Candy Crowley, the veteran CNN reporter.

For Obama, the challenge is to be more aggressive in combating his Republican rival during the town hall-style debate, which often requires candidates to also show empathy with the questioner.

Campaign officials insisted they were more focused on substance over style.

'The question is not just which candidate connects with the questioner, but who has the better policies for the American people for the next four years,' Psaki said. 'On that front the president has a great advantage.'

But Romney's team claimed the advantage Sunday, citing polls that suggest the race is essentially a tossup.

After attending church services Sunday morning, the Republican candidate devoted several hours to debate practice at a hotel near his suburban Boston home. Romney, who has been setting aside time for debate practice since June, was joined by his senior strategy team, including Ohio Sen. Rob Portman, who has been playing Obama.

'I think the wind is at Gov. Romney's back and we're clearly on momentum,' Gillespie said. 'This is going to be a close race. I knew that when we were behind in the polls. I know it now when we're ahead in the polls.'

Gillespie made his comments on 'Fox News Sunday'; Gibbs appeared on CNN's 'State of the Union.'