He also defended his record on Iraq and Afghanistan, and argued that drawing down the wars there allowed him to refocus the administration's attention on "who actually killed us on 9/11." Later, he delivered a personal anecdote about what the death for Osama bin Laden meant to a 9/11 victim's daughter, while reminding voters of a 2008 quote in which Romney said he wouldn't want to "move heaven and earth to get" Osama bin Laden.

Romney, who congratulated the president for "taking out" bin Laden early on in the debate, also agreed with the president on his administration's use of drone strikes, and said "we should use any and all means necessary to take out people who pose a threat to us and our friends around the world."

Both candidates seized on any opportunity to discuss their domestic policy issues, circling back to the economy, taxes and education at any available turn. Mr. Obama invoked Romney's 2008 opposition to bailing out the auto industry and reiterated his accusation that "the math doesn't work" for his economic proposal; Romney, meanwhile, touted his record on education during his tenure as Massachusetts governor.

The debate, at Lynn University in Boca Raton, Fla., was divided into six 15-minute segments. According to an instant poll taken immediately following its conclusion, Mr. Obama scored a clear two-to-one victory against Romney, with 53 percent of respondents giving the debate to the president and just 23 percent calling it a win for Romney. Another 24 percent felt the debate was a tie.

Meanwhile, a CBS News poll released just hours before the debate showed Mr. Obama leading Romney by a 9-point margin on foreign policy. Likely voters also viewed Mr. Obama as stronger on terrorism and security: 49 percent said Mr. Obama would do a better job, and 42 percent said Romney would. On U.S. policy toward Iran, Mr. Obama edged Romney 46 percent to 43 percent among likely voters.

On U.S. policy toward China, a frequent Romney discussion point on the campaign trail, the two candidates are even at 44 percent. On Israel, Romney has an edge over the president, with 46 percent to Mr. Obama's 42 percent.

Mr. Obama also holds a lead on which candidate would better handle an international crisis: 38 percent of likely voters said they had a lot of confidence in him to do so, compared with 30 percent who expressed the same level of confidence in Romney. Still, a majority of voters express at least some confidence in both the President (62 percent) and Romney's ability (58 percent) to handle an international crisis.