A man like John McCain is utterly lost once he turns against himself -- you can see it in the his face. There's an ugly vacuum where once there was a solid core.
A friend of mine once joked that in order to pull off a successful booty call, there are two things you absolutely can't do. I bring this up because apparently no one ever told John McCain these essential rules.
I personally would emphasize the lateness of McCain's attacks, and that it is a character flaw to offer exaggerated and unsupported allegations against your opponent.