The town hall format of Tuesday's presidential debate may make a comeback difficult for President Obama, say political experts, because taking questions from real voters instead of a professional moderator could restrain Obama at the very moment his supporters want him to be more aggressive against Republican Mitt Romney.

Obama has watched his lead over Romney all but evaporate since their first meeting in the Oct. 3 debate in Denver, after Obama's listless defense of his first term was universally panned.

Hoping to reverse his fortunes in the second debate, Obama spent the past several days hunkered down in Virginia in intensive preparations for the face-off at Long Island's Hofstra University.

Second presidential debate
What: Town-hall style format
When: Tuesday, 9 to 10:30 p.m. EDT
Where: Hofstra University, Hempstead, N.Y.
Who: Moderator is CNN's Candy Crowley

Campaign aides have promised a more aggressive posture from the president, but the obstacles he faces this time include not just Romney but the debate's format.

In the first presidential debate and last week's vice presidential face-off, a single moderator guided the conversation, giving the opponents ample opportunity to go after each other. But having regular voters in the audience asking the questions Tuesday could make it difficult for Obama to pivot and attack Romney the way Democrats believe he must.

The town hall debate format, first used in presidential politics in 1992, was once considered the more unpredictable forum, a true risk for candidates. But the town hall format this year could be the most restrained -- and constraining -- political observers said.

"It's a harder format for Obama to go after Romney," said Pat Caddell, a pollster for former President Jimmy Carter. "If he gets really mean, it will help Romney."

Obama's supporters were elated after last week's vice presidential debate, when Vice President Biden regularly interrupted Republican Paul Ryan or laughed aloud during Ryan's responses. Campaign aides and Obama supporters left the debate hall that night convinced Biden's performance should guide Obama in Tuesday's debate. Others say it's better for Obama to refrain from mimicking Biden.

"For presidents, it's OK to be proactive, but being outwardly aggressive toward your opponent, especially in a town hall setting, could be a little bit dangerous," said Reed Galen, a deputy campaign manager for former Republican presidential nominee John McCain.

In a 2000 presidential debate, then-Vice President Gore was pressing Republican George W. Bush on whether he supported a health insurance bill pending in Congress. While Bush was responding, Gore strode toward Bush's podium. The stunt, Galen said, was awkward and made Gore look silly, not tough. Obama has to avoid the same kind of miscalculation, he said.

"One of the things this president really has going for him is he is likable," Galen said.

If he avoids being overaggressive, Obama could have an edge in the town hall format, given the perception that Romney, a wealthy businessman, can't relate to the average American, analysts said.

During the first town hall presidential debate in 1992, President George H.W. Bush was asked by a voter how the recession affected him personally. His hesitation in responding came across as excruciating and confirmed for many their suspicions that Bush was out of touch with regular people.

The town hall format could still be "very pleasant for Obama," said Marc Landy, a political science professor at Boston College. "He's probably a little better at relating to ordinary people than Romney."