Obama's performance was, frankly, anemic. I don't care about stupid stuff like him looking down at his notes a lot, or sounding "confident". I know that's not Obama's style, and though I don't like it, I came to terms with it a long time ago. But what I wanted Obama to do was nail Romney on his lies, force him to have to defend the garbage from his campaign, and he never did.
Obama never effectively responded to the $716 billion remarks on Medicare. He let Romney have the last word on Dodd-Frank regulations. He let Romney say 20 million people would lose their insurance under the ACA and never challenged the claim. He never went after Romney on Bain. Never went after Romney on Romneycare, or his remarks on it being a national model. Never went after Romney on the 47 percent comments. He simply NEVER attacked. It was frustrating.
It made it seem like Obama didn't care. If he doesn't care enough to put on a good showing during the debate, if he doesn't believe the presidency is worth fighting for, or that Romney, if elected, would further hurt the middle class (or perhaps doesn't care enough about the middle class to prevent it), I'm sure some will ask why he should even have their vote.
I don't think this performance will have a huge impact on the race. Romney will certainly have a bounce of some kind, but as has been said many times, the debates don't matter much. People's minds have been made up, and were made up a while ago. Still a bomb from Obama though.