I'm not quite sure about this; Obama being defeated at what he usually excels does not bear well for him even if he still leads the polls.
Obama has never been an incredible debater, to be honest. He managed to beat McCain in '08 but that was only after about 9,000 debates with Hillary Clinton (and MSM declared him the loser of at least 8,000 of them).
People have very short memories... He beat McCain because McCain was only slightly worse than he was.
Also, Obama's not done a debate like this for 4 years.