Depends on just how heinous the attack was.
In the immediate aftermath of 9/11, there were in fact voices that said that Bush had created the attacks himself because the press was about to finish its own Florida recount and show that Gore was the legitimate president. Those voices were restricted to the Internet. No one in the Mainstream Media or Congress took the chance of uttering those words.
Don't count on Kerry or anyone else who understands political expedience taking the enemy's side after a future attack.