McCain hasn’t shown any interest whatsoever in destroying Obama (or Clinton). Why will the rest of the country?
That will be up to the GOP-aligned 527 groups. They have a nice body of material to work with already, and there's probably more to come. Keep your campaign contribution cash ready to support them.
The 527s will swift-boat Obama to kingdom come. Captain McQueeg will deplore the negativity and try to remain above it all, as the Donks and the drive-bys hurl charges of racism.