[Mitchell]

What if he resigned, essentially ceding Iraq, but went underground, maintaining control of his WMD and conducting a terrorist war? It would place us in a very difficult situation. What would we do?

[piasa]

went underground, maintaining control of his WMD and conducting a terrorist war?

That's what he has effectively been doing... the only new wrinkle is the resignation, but that's just paper. From the noises coming from Rumsfeld, in order for the US to even consider him 'resigned,' he actually has to physically leave Iraq.