Here's TPM Editor Josh Marshall on what happened.
The first half hour was a draw, though President Obama scored by default when Romney either didn’t or couldn’t attack on Libya.
After that though Romney began to falter as Obama became more direct, organized and declarative. Romney seemed increasingly lost. Obama seemed comfortable, happy. The visuals told the story. Romney was sweating a lot and looked like he was in pain. Into the second half of the debate Romney’s answers seemed more jumbled and unfocused. There was even the rambling and generally uncontroversial digression on Pakistan. Why? He seemed lost.
Translated into Romney visuals he had what President Obama had in the first debate: that look of someone who wanted to be anywhere but on that stage.
This is why Mitt Romney didn't want to talk about foreign policy. He clearly doesn't know what he's talking about. He wants to criticize every action taken by President Obama, but he can't actually describe his own plan of action on Iran, Libya, China, or Russia...
Obama took the chance to needle Romney on his adversarial position on Russia. “I’m glad that you recognize al Qaeda is a threat. Because a few months ago when you were asked the biggest threat facing America, you said Russia,” Obama said. “The Cold War has been over for 20 years. But governor, when it comes to our foreign policy, you seem to want to import the foreign policies of the 1980s, just like the social policies of the 1950s and the economic policies of the 1920s.”
Later Obama said directly to Romney, “You indicated that we shouldn’t be passing nuclear treaties with Russia, despite the fact that 71 senators, Democrats and Republicans, voted for it.”
... Or anywhere else.
So instead, he wanted to talk about how much he loves teachers. Oh, and he wanted to throw out more G-O-TEA talking points on the economy.
And this comes back to the whole issue of "The Commander-in-Chief Test". How has Mitt Romney proven himself in that test? Has he even tried the test? How can he be President if he can't explain his vision of presenting America to the rest of the world?
And herein lies (another reason) why Mitt Romney still struggles in this campaign.