President Obama and Mitt Romney meet tonight in Boca Raton, Fla., for their third and final presidential debate, and the stakes couldn't be higher: The polls show the race in a dead heat, and the debate is likely the last event that could dramatically alter the contest's trajectory. Under pressure to defend his record and solidify his foreign-policy edge, Obama will undoubtedly underscore the killing of Osama bin Laden. For his part, Romney must convince voters that he would make a credible commander-in-chief, while seducing independent voters with an alternate national security vision. Here, a guide to where the candidates stand on key issues:

1. Libya
The biggest chink in Obama's foreign-policy armor? The September terrorist attack on the U.S. Consulate in Benghazi, Libya. The White House's response to the attack has been confusing, and Republicans have accused the administration of misleading the public. Romney sought to exploit this advantage, but only hurt himself by appearing to politicize the death of four Americans. His dilemma tonight: To back off Benghazi or go on the offensive? "The national conversation has been about the terrorist attack in Benghazi," says Peggy Noonan at The Wall Street Journal. "Did the president tell the truth at the time?" But Romney was caught "playing political gotcha with a national tragedy," says Bill Keller at The New York Times, and another miss could badly hurt his campaign. Obama's job is to make sure "the political spin stops," says Juan Williams at The Hill. "The bottom line is there is no evidence so far to support the Romney camp's claim of incompetence or a cover-up."

2. The Arab Spring
Romney has heavily criticized Obama for his handling of the Arab Spring, suggesting that stable, pro-American regimes would have emerged following the fall of dictators in Egypt and Libya if the president had taken a firmer hand. While it's unclear what Romney would have done differently, Spencer Ackerman at Wired summarizes the debate thus: "[Does the U.S. need] to involve itself deeper in the Arab Spring; pick favorites within the uprisings; or stand back as the upheaval proceeds?" Obama is under pressure to defend his hands-off, country-by-country approach, while articulating a broader foreign policy argument that explains why "he'll intervene in Libya but not Syria," says Ackerman. Romney, for his part, "has yet to distinguish his geopolitical plans from Obama's without seeming like he's out to start a whole new war."

3. Iran and Israel
Romney has hammered Obama for failing to halt Iran's suspected progress toward a nuclear weapon; this dovetails with Romney's claim that Obama hasn't been a good friend to Israel. However, both candidates essentially have the same policy: A stated determination to prevent Iran from obtaining a nuclear weapon, and a vow to keep all options — from diplomacy to military force — on the table. Romney is having so much trouble distinguishing himself from Obama that he ends up sounding like a "foreign policy love child" of Obama and George W. Bush, says Sally Kohn at Salon. "Rhetorically, Romney sounds almost exactly like George W. Bush. In terms of what he'd do on the ground in places like Iran [however]... Romney sounds exactly like Barack Obama." Unless Romney can convince voters that his policies to stop Iran and protect Israel are distinct from Obama's, says Keith Koffler at Reuters,the president will continue to enjoy his healthy advantage with Jewish voters.

4. Afghanistan
Afghanistan is another area in which Romney has struggled to differentiate himself from the president. Romney says "he would hew to President Obama's timeline to withdraw U.S. troops by the end of 2014," says Maeve Raeston at the Los Angeles Times, "but he would part ways with the president by giving greater deference to the judgment of military commanders." However, it remains unclear what Romney would do if the military's top brass called for keeping U.S. troops in Afghanistan past 2014. Obama has used Romney's "past statements to argue that Romney's commitment to Afghanistan could be open-ended," says Raeston, which could be a problem for the 60 percent of voters who favor a speedy withdrawal from the country.

5. China
Here, Romney and Obama have real differences. Romney has vowed to dub China a "currency manipulator" on his first day in office, a designation that would almost certainly spark a self-defeating trade war. Romney "wouldn't be the first candidate to pummel China on the campaign trail and make nice in the White House," says Keller. "But the stridency of [his] protectionist rhetoric…makes many of [his] supporters cringe." Indeed, the U.S. Chamber of Commerce, the country's largest business lobbying group, opposes such a move. However, polls show that "Americans have turned increasingly negative toward China and its trade policies," says Howard LaFranchi at The Christian Science Monitor, which means Romney may be on the right track, politically speaking. Obama's challenge is to sound suitably tough on China without alienating one of the U.S.'s largest trading partners.

6. Defense spending
Romney has claimed that the "U.S. military is in danger of becoming a 'hollow force' under Obama because of potential cuts," say Indira A.R. Lakshmanan and Margaret Talev at Bloomberg. Romney has proposed reversing a planned $1 trillion in Defense Department cuts and adding another $1 trillion in spending over the next 10 years, measures he argues are necessary to ensure American military superiority. Obama is also opposed to the cuts, but has shot down proposals to boost military spending after that, saying it's simply unaffordable. The fight over defense spending is one of the few areas of the debate that will touch directly on domestic policy, with the candidates outlining their priorities when it comes to reducing the budget deficit.