Usually they just vote for his speaking style. They weren’t entertained by the rhetoric style of Bush and McCain. They vote for president in the same way that they vote for American Idol.
Oh, I think I’d be a bit more respectful of them if they actually admitted that they thought he was the better candidate because he gave a better speech.
But NO... they know that this makes them look shallow and ignorant, so they try to claim that he had superior positions on issues and a better grasp of them. Of course they can’t even NAME an issue that he talked about much less what concrete position he took on that issue...