President Barack Obama enters his second debate Tuesday against Mitt Romney looking to regain his footing and determined to prevent the Republican challenger from scoring another strong debate performance that could further revitalize the GOP presidential nominee's campaign.

And, by all indications, both candidates are braced for a spirited encounter.

The rhetorical fireworks that had been absent in the first debate on Oct. 3 in Denver between Romney and Obama are almost certain to appear at the second of three presidential debates this fall, this outing set for 9 p.m. ET on the campus of Hofstra University in Hempstead, N.Y.

The Obama campaign has sent signals that the president has every intention of actively challenging Romney onstage this evening, frustrating the GOP candidate's efforts to appeal to independents and moderates the way the president hadn't been able to in their first debate.

Romney, meanwhile, has hopes that a second straight positive debate showing would add further momentum to his campaign. The former Massachusetts governor trailed Obama before the Denver debate, but Romney's strong outing has breathed new life into his campaign. A slew of national and state-level polls that have shown a tighter race for the White House in the 13 days since that first debate, with Romney pulling even — or even ahead — of Obama in some polling.

With Tuesday's second presidential debate looming, both candidates spent Monday hidden from the media. President Obama geared up in Virginia while Mitt Romney stayed near his home in Massachusetts. NBC's Chuck Todd reports.

"I know no debate is ever the same and it's going to be fun to watch — maybe more fun for you than for me," Ann Romney said Monday in Pennsylvania about her husband's preparations for the second debate, "but one thing I know for sure: Mitt's prepared, Mitt's confident, Mitt's got a good presence about him, and Mitt's running because he believes in America."

First Thoughts: Why tonight's debate could be so crucial

The Romney resurgence and Democratic handwringing about the president's low-wattage performance in the first debate have prompted a shift in Obama's tack. Democrats almost universally hope for and expect a feistier performance by the president on Tuesday, a shift in strategy that has been telegraphed by the Obama campaign.

A campaign source, for instance, told NBC News on Monday that the president planned to bring up Romney's disparaging comments about the "47 percent" of Americans he said wouldn't vote for him because they depend on government. Obama declined to use this and other potent cudgels against Romney in the first debate.

"I think he's going to be aggressive in making the case for his view of where we should go as a country," Obama campaign senior adviser David Axelrod said Sunday on Fox in anticipation of the debate. "I mean, we saw Governor Romney sort of serially walk away from his own proposals and certainly the president is going to be willing to challenge him, on it, as we saw the vice president challenge Paul Ryan."

RNC Chairman Reince Priebus talks about the Romney campaign's ground game and why the GOP is doing a better job in this election than they did in 2008. Priebus also discuss absentee ballots and which swing states could decide the election.

The potential for a contentious showdown on national television could transform the second debate into another turning point in the 2012 campaign.

Romney and Obama each holed up for much of the weekend and through Monday to practice for the second debate, which is moderated by Candy Crowley of CNN. She'll serve as the mediator between the candidates and also the audience in this town hall format, where audience members will pose questions of the candidates.

FEATURED: Questions from readers for the second debate

Obama prepared for the debate at a resort in Williamsburg, Va., retreating from the White House much as he had before the first debate, when he studied for the occasion in Nevada.

For his part, Romney has squeezed in debate preparations around his campaign schedule, as Ohio Sen. Rob Portman — who plays Obama in mock debates — appears to have assumed a broader strategic role.

What is clear about the second presidential debate is that several factors that allowed Romney to be successful at the first debate will have changed in tonight's contest.

Vice President Joe Biden's aggressive posture in last week's debate versus GOP vice presidential nominee Paul Ryan suggested that the Obama team won't shrink from a fight in the remaining debates.

While the format is different, Crowley might not be inclined to allow Romney talk past her instructions as the Republican frequently did to moderator Jim Lehrer in the first debate.

RELATED: Obama will try to bend town hall format to his advantage

Senior Obama advisor and former White House Press Secretary Robert Gibbs previews Tuesday's debate and says President Barack Obama will give an exceptionally strong, passionate performance and lay out his agenda for the future.

And, the candidates will have to interact directly with the voters who will be asking the questions. While the queries will be selected by the moderator, the voters will directly deliver them to the candidates, creating a less formal atmosphere.

The issue profile is sure to be more expansive, too. While Libya and other topics of foreign policy didn't make an appearance in the first Obama-Romney event, they're almost sure to in this second outing. Other topics — from housing to education to immigration — could also threaten to trip up either candidate.

The most important difference might arguably be in Obama, who if nothing else has vowed to cast off the lethargy that plagued his first outing.

Obama himself told a radio host on Oct. 10 that he was "too polite" toward Romney in their first meeting.

"I think it's fair to say that we will see a little more activity at the next one," he said.