The much-discussed attacks on McCain begin with some fairly sober stuff from Missouri Sen. Claire McCaskill. "We tried tax cuts for the rich! We did everything big oil asked! Come on, America!"
I think the most successful convention attacks are mockery: George H.W. Bush was born with a silver foot in his mouth, John Kerry will defend America with spitballs, etc. This sounds like exasperation, or desperation, or both.