The confrontational tone of the first two debates also returned - this time, initiated first and more forcefully by Obama. At one point, he told Romney, "Every time you've offered an opinion, you've been wrong" on recent foreign-policy matters.
Romney retorted that Obama's criticisms weren't enough: "Attacking me is not an agenda."
Romney offered specifics for how he would tackle Iran's nuclear program, saying he would seek to have Iranian president Mahmoud Ahmadinejad indicted by a world court for inciting to genocide. Romney said he would also seek to have Iranian diplomats made pariahs around the world, isolating that country diplomatically in the way that South African diplomats were isolated under apartheid.
But often Romney sought to steer this foreign-policy debate toward subjects more central to his campaign: the economy, and his plans to streamline the U.S. government.
Later, however, the debate returned to its announced subject. Romney criticized Obama for allowing the number of ships in the U.S. Navy to shrink to the lowest number in decades. Obama retorted with a line he just might have rehearsed, telling Romney that he might not understand the military.
Romney, in the debate's first minutes, seemed to be less fiery than in past debates. At several points, he said he'd agreed with Obama on foreign-policy decisions, including Obama's urging that Egyptian President Hosni Mubarak leave power last year. He said that Obama should have done more to help Mubarak adapt to growing pressure for democracy. But, Romney said, "Once (Egypt) exploded, I felt the same as the president did."
The 90-minute debate began at 9 p.m. at Lynn University in Boca Raton, Fla. Going in, the two candidates seemed likely to renew their arguments over Obama's handling of Iran, China, the civil war in Syria, and the attack in Libya that killed four Americans last month.
For both, this could be their last best chance to break a close race open.
A new Washington Post-ABC News poll, out Monday, showed that Obama and Romney are effectively tied, with Obama leading by just one percentage point among likely voters, 49 percent to 48 percent.
The poll shows that Romney has gained significantly on the subjects of international affairs generally, and handling terrorism specifically. At the end of September, Obama held an 11-point lead over Romney as the candidate voters trusted on terrorism.
But now, 47 percent side with Obama on the issue, 46 percent with Romney.
The president's debate sparring partner, Sen. John F. Kerry, D-Mass., offered a preview of President Obama's likely line of attack during a brief talk with reporters in the spin room at Lynn University, saying "tonight's the night of reckoning" for Romney's shifting positions on U.S. foreign policy.
"You can't just come in here tonight and be a different Mitt Romney," Kerry said. "You can't Etch-a-Sketch your way through foreign policy. You have to have some consistency and precision and it doesn't hurt to have a little bit of experience, instead of none."
Kerry called Romney and his vice presidential running mate, Rep. Paul Ryan, R-Wisc., "the most inexperienced twosome in modern U.S. history to run for president and vice president. They have zero experience in foreign affairs, and there is a lack of clarity in almost anything they've said."
"Romney's campaign is trying to say that if he just comes out there and shows he's competent, he'll be okay. No, that's not the standard for commander-in-chief," Kerry said. "When I stood up there with George Bush I had to show I had better ideas and show I had specificity. . . Well, tonight you have to judge the specificity. What does he want to do in Iraq, what does he want to do in Iran?"
Kerry even took a shot at Romney's summer foreign trip to Britain, Israel and Poland, a jaunt punctuated by several perceived gaffes. Romney offended the organizers of the London Olympics when he questioned whether they were prepared to stage the games and he stated that the sluggish Palestinian economy is plagued more by "cultural" differences than by the strictures of the decades-old Israeli occupation.
"He takes a trip overseas and he trips all over himself from country to country," Kerry scoffed.
Kerry played the role of Romney during Obama's secret prep sessions for all three debates, chosen for his familiarity with Romney's record as Massachusetts governor and his own experience in the 2004 presidential debates when he was running against then-President George W. Bush.
Ahead of the debate, Obama's campaign released a new online ad touting the president's efforts to withdraw troops from Afghanistan and Iraq. "It's time to stop fighting over there, and start rebuilding here," the ad says. It attacks Romney for opposing the withdrawals.