It was a debate of expectations.

Many expected the President to blow him out of the water and when he didn't, the expectations were unfulfilled. It's simply not the nature of the President to act in such a way. Many supporters were disappointed.

With Romney, expectations were much lower. It didn't matter that he contradicted many of the things he has been running on for quite a while. It didn't matter if he flip-flopped on the tax issue. He was aggressive and demanding of the last word every time. He got his way and his supporters are thrilled with his performance. He exceeded all their expectations.