Is it possible that the reason the Democratic candidates are ignoring McCain and the wider effects of their bickering is because they don't see the election as a race between Democrats and Republicans? Most polls suggest that dissatisfaction with the GOP is so high, that it won't matter who they put forward as a candidate, as the Democrats are a shoe-in. It's possible that this has led Obama and Clinton into narrowing the race until it is just a battle between the two of them, ignoring McCain completely. They're certainly expending an awful lot of energy, money and vitriol towards each other, that might ordinarily only have come out in the national election.
Also, can pundits please stop saying that only racist people don't like Obama? At this point, I'm fed up of both Democratic candidates - does that mean I'm a racist chauvinist? No. I'm not. I think either of them would be a good president (same goes for McCain), but I don't think we're going to have a great 44th president. By constantly mentioning his race, there is no way he can run the "post-racial" campaign that everyone keeps talking about. Treat him like any other candidate, who happens to be intelligent, highly organised and full of potential. Then at least Clinton won't be able to say he's received a free-ride.*
The Democrats are setting themselves up for the mother of all disappointments by building Obama up into a messianic figure of liberal salvation. It's dangerous, and will ultimately leave everyone feeling cheated or let down - there's no way anyone can live up to the expectations people have piled on top of him (not his fault, but he'll get the blame).
* Speaking of which, I think McCain would have a genuine beef about the Democrats receiving all the media coverage. Though, at the same time, he might benefit from it because by the time people come round to voting, they'll be so sick of both Clinton and Obama that they might just pull the lever for McCain who is, let's be honest, a good prospect. He'd be just as good in the White House as the Democratic candidates, if not better, because he won't have spent the last year tearing his party a new one.