The Romney campaign would not comment about follow-up questions.

Asked if the campaign prefers no follow-up questions from Crowley, Psaki said: “I’m not going to get into any more specifics than that.”

Despite losing his lead after the first debate, Obama has some history on his side. Incumbent presidents, notably Ronald Reagan in 1984 and George W. Bush 20 years later, lapsed in their first debates. Like Obama, they’d grown used to deference even opponents show to the president of the United States, and they seemed taken aback at the kind of onslaught they hadn’t endured since their last campaigns four years earlier.

Reagan and Bush recovered in their second debates and went on to win their re-election bids. But they were running when the economy was thriving, and Obama is not. Obama’s fate is more difficult to handicap, as he’s being tugged by two conflicting historical forces – the sluggish recovery has kept his popularity down, but it’s not dismal enough to make him an underdog.

Both candidates face new challenges Tuesday. Republicans sense this is their first big chance to question Obama’s national security policy, a topic that didn’t come up in the first debate.

For Obama, it could be Libya. His administration stumbled in explaining circumstances surrounding the death of four Americans, including the U.S. ambassador, in an assault on the U.S. consulate in Libya last month.

Vice President Joe Biden added to the controversy, saying during his debate last week with challenger Paul Ryan that the White House was unaware embassy officials wanted more security. That seemed to contradict congressional testimony earlier in the week, when a State Department official told Congress that she had received requests for more security in Benghazi but that she turned them down because the department wanted to train Libyans to handle the duties.

For Romney, it could be his claim that he’ll be able to cut tax rates enough to stimulate growth but also able to limit unidentified deductions so that the wealthy end up paying the same amount of taxes.

Independent analysts have been skeptical of the claim. Congress’ bipartisan Joint Committee on Taxation staff reported Friday that even eliminating most tax breaks would only support a 4 percent reduction in rates. The Romney campaign called the finding “irrelevant,” saying it did not account for the growth that rate reductions would spur.

Obama also has another tricky task: He has to make a fresh appeal to the small slice of undecided voters who could decide the election. They usually have doubts about the incumbent but are getting to know the opponents. They need time to assess whether they can envision Romney as president.

"It’s harder for an incumbent to recapture votes from people who have jumped off his ship. Those people have begun to say, OK, I’m comfortable with Romney," said Brad Coker, managing director of Mason-Dixon Polling & Research, which conducts surveys in several states.