If it were almost anyone other than Romney I would agree with you.
It's an issue for sure. But the fact is I've never seen the level of....derangement... when it comes to a sitting President. Cons loved to joke about BDS, but it's pretty clear that if something like that was possible they're suffering from ODS hard. The good news for Mitt is that level of lunacy will mean turnout. It'll be an ugly mean crowd, but they'll come out. Bush brought out some ugliness in the left, but Obama...man oh man....
The real question for Obama is will his crowd turn up? Paul Ryan may scare them enough to show up, but the truth is his base isn't coming out to vote for him either. He's done enough to piss off liberals that if there had been a fight at the Democratic Convention, he might have had some troubles holding his spot on the ticket.