Obama's not the best speaker in the world, but he's not bad. He's also intelligent and personable and, overall, has a decent head on his shoulders.
Mitt is an awful speaker. All his speeches sound like memorized soundbites with the occasional "America is the land of freedom, apple pie, hard work... America...the Beautiful..." I honestly wish him luck because I know how awkward he can be. The only reason he survived the GOP debates was because his competitors were almost certainly mentally retarded. Perry? Cain? San-fvckin'-torum? These guys were clowns. You can say all you want about Obama - he's a nazi, he's a socialist, he hates America... blah, blah... but you can't say he isn't intelligent. Mitt Romney will have to rely on accusation and name-calling to appeal to the emotional GOP base, but he won't be able to out-debate Obama. It just won't happen. He's not intelligent.
Good luck, Mitt.