None of the attacks have really stuck, up to this point. What do they now have that is so powerful, that it will stick? It seems to me that politicians do not save their best ammunition for a late point in the campaign, when they already are far behind.
It makes no sense for the McCain campaign to save it's best attacks for the tail end of the fight, when they are losing. They logically would have used those attacks to gain an advantage earlier.
Or are these coming attacks so utterly shameless and low that only a desperate candidate would employ them?