BURLINGTON, Mass. -- As Mitt Romney's campaign claimed new momentum in the race for the White House, President Barack Obama's political advisers Sunday promised that the incumbent would unleash his more aggressive side in Tuesday's debate to prevent their Republican rival from delivering another "magical and theatrical performance."
Mr. Obama and Mr. 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 Mr. Romney bested Mr. 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 Mr. Obama's adjustments: "The president can change his style. He can change his tactics. He can't change his record."
On the eve of their second debate, the two rivals remain locked in a virtual dead heat nationally, with Republicans showing increased enthusiasm for their nominee after his big win in the first debate, according to a new Washington Post-ABC News poll.
Likely voters in the new poll split 49 percent for Mr. Obama to 46 percent for Mr. Romney, basically unmoved from the poll two weeks ago, just before the two candidates met in Denver for their first debate. On topic after topic, the survey portrays an electorate that remains deeply divided along partisan lines and locked in its views.
But more people changed their views of Mr. Romney, largely in a positive direction. Overall, more than twice as many say their opinions of the former Massachusetts governor improved than say they worsened as a result of the debate. The strongest reaction is among Romney backers, 70 percent of whom say the Denver debate made them think more highly of the GOP nominee.
The telephone poll was conducted Wednesday through Saturday among a random national sample of 1,252 adults. Results for the full sample of 1,063 registered voters are plus or minus 3.5 percentage points; they are also 3.5 points for the 923 likely voters.
Meanwhile, the father of Christopher Stevens, the U.S. ambassador to Libya who was killed in the attack in Benghazi last month, told Bloomberg News his son's death shouldn't be politicized in the presidential campaign.
"It would really be abhorrent to make this into a campaign issue," Jan Stevens, 77, said in a telephone interview from his home in Loomis, Calif., as he prepares for a memorial service for his son.
Mr. Romney has criticized Mr. Obama for not providing adequate security in Libya, saying the administration has left the country exposed to a deadly terrorist attack.
The ambassador's father, a lawyer, said politicians should await the findings of a formal investigation before making accusations or judgments.
The question of whether the embassy attack and the ambassador's death are being politicized came up on several Sunday morning television talk shows.
Obama campaign strategist David Axelrod said on "Fox News Sunday" that Mr. Romney is "working hard to exploit this issue."
Mr. Gillespie said on the Fox program that the country needs "honest and accurate answers."
"What we have seen is a constantly shifting story from this administration," he said.
Mr. Obama spent the day Sunday with aides in swing state Virginia, while Mr. 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.
Mr. 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, Mr. 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.
"I think Mitt Romney's performance was, indeed, magical and theatrical. 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," Obama senior campaign adviser Robert Gibbs, appearing on CNN's "State of the Union," said of the first debate.
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 today, either absentee or in-person early voting has begun in 43 states.
Mr. 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 Mr. Ryan said recent victories, including the failed recall of Gov. Scott Walker, have it poised to deliver for both Mr. Romney and Mr. Thompson in just over three weeks.
Obama aides said the president was clear-eyed about the need to have a better showing in his second debate with Mr. Romney. After a listless first performance, Mr. 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.
As for Mr. Romney, the Republican candidate devoted several hours to debate practice at a hotel near his suburban Boston home after attending church services Sunday morning. Mr. 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 Mr. Obama.
The Washington Post and Bloomberg News contributed.