He meant to flatter the actor (who has played a President), but oh, what slipped out!
ADDED: Does it make it better or worse that he goes on to say, "This guy was God before I was"? (Freeman played God in "Bruce Almighty.") This wasn't a planned comedy routine, but an ad lib. Maybe it would have been really funny if you heard it delivered. I think the "God" line was an attempt to save himself after the first line came out wrong. And if you look at it the right way, it's even kind of self-effacing, mocking the people who act like Obama is God. But candidates should probably avoid saying such weird things.