According to CNN, President Obama won the debate 48% to 40%. It's not that big of a margin. But one thing was readily apparent: in a debate on foreign policy, the commander in chief has a built in, almost insurmountable advantage. And that showed in this debate.
In a strategic sense, I think Romney walked away from this debate satisfied with his performance. He was playing a different sort of prevent defense. His debate strategy was to mollify and reassure the independent while he was content to let Obama play as attack dog.
In my own biased opinion, I thought that was unpresidential. A sitting President should talk about his policies and his deeds, not nitpick the statements of his challenger. He sort of stooped down to a challenger's level whereas he should have been trying to fend off Romney from climbing up to his.
The debate was undoubtedly a tactical victory for Obama. I think it was a strategic victory for Romney. It is extraordinarily difficult to unseat a modern President precisely because the office is overexposed. The President is in front of a camera every day of every week. People get used to watching his image in their television and computer screens. And challengers aren't going to be able to defeat an incumbent until two conditions are satisfied. 1: voters are in the mood for a change. 2: voters are confident that the challenger represents a safe change.
The first debate was a game changer. The last two were relative draws, much more in line with the history of debates. It's now up to each respective campaign to get out the vote and push their candidate over the top. Currently this is an extremely tight race. It seems likely to remain so all the way to election day.