Think of it like this: every time Obama says "uh" on camera, what he's really doing is flinching from the possibility that his campaign manager, David Plouffe, is going to whack him on the nose with a newspaper. Again. Hence the stutter.
Hitch writes that he's getting the feeling that Obama is a little scared of winning this contest. And why wouldn't he be? After two years of dancing to his minders' tune, being reduced to a mouthpiece for smarter, more experienced and more ambitious men and women, he can look forward to at least four more! This is an understandable fear.
But Obama's also feeling what a child feels after he has climbed into Daddy's truck and turned it on, believing that he's seen Daddy do it so many times that he can do it too. The Obama campaign truly has been the campaign of hope: as in, "I hope I can do this." Things are rolling now, but it's just starting to dawn on him that maybe he doesn't know as well as he thought how to control this thing. He's more likely to come to a screeching, crunching, grinding stop than to make a graceful finish.