But Romney has vulnerabilities. For one, the president can respond to his Libya criticism by playing the commander-in-chief card, as he did in the second debate: The notion that the Obama administration played politics or purposely misled the public over the attack, the stone-faced president said, is "offensive." That argument underlines the president's core foreign policy argument against his rival, which boils down to this: I'm out here making the hard choices - including ordering the mission that took out Osama bin Laden - while you take potshots from the sidelines.

Mr. Obama has tried to use Romney's attacks on his foreign policy diplomacy against the Republican nominee, saying that Romney and his running mate Paul Ryan want "to take us back to an era of blustering and blundering so dearly." That's a potentially resonant argument to a war-weary public, and Romney has given Mr. Obama ammunition to make it: As Mr. Obama likes to note, Romney labeled Russia "our No. 1 geopolitical foe."

"You don't call Russia our number one enemy - not al Qaeda, Russia - unless you're stuck in a cold war mind warp," Mr. Obama said at the Democratic National Convention. The president added a knife-twisting reference to Romney's gaffe-plagued foreign trip: "You might not be ready for diplomacy with Beijing if you can't visit the Olympics without insulting our closest ally." Mr. Obama may also point out that many of Romney's foreign policy advisers have ties to the Bush administration.

"When Romney attacks Obama for diplomacy, Obama can just say, 'if you think it's a bad idea to try to get along with people, go ahead and go back to George W. Bush and see how that works,'" said O'Hanlon. "I think that just plays into Obama's hand."

In a memo released at midnight by the Obama campaign, Sen. John Kerry previewed the president's attacks, writing that Romney "offers nothing but endless bluster and a record of dangerous blunders, failing at every turn to show he's up to the challenge...He is an extreme and expedient candidate who lacks the judgment and vision so vital for the Oval Office, and he's at the top of the most inexperienced foreign policy ticket to run for president and vice president in decades."

For Romney, who does indeed lack foreign policy experience, the goal Monday night will be in part to make voters comfortable with the idea of him as commander in chief. Foreign policy is not Romney's strength, and while he has been huddled with his foreign policy advisers in advance of the debate, there's no denying that he is on firmer footing when the topic is the economy.

Romney laid out his foreign policy vision during a speech in Virginia earlier this month, where he called for more arming of rebels in Syria, said he would tighten sanctions on Iran and said he would improve the U.S. relationship with Israel. Romney has at times struggled to differentiate his foreign policy plans from those of the president: On Afghanistan, for example, he says he supports the 2014 timeline for U.S. withdrawal of troops but opposes the fact that the president set the deadline.