If I had some Gannon-like magic access to the press briefing, I'd ask Scotty:
If Rove and Libby lied to you and played you like a fool, sending you out to repeat lies in good faith, you should be outraged enough to resign. If the lies were your own, and you've been caught standing behind the presidential seal telling untruths of your own volition, you should resign out of shame. So why are you going to resign, Scotty, outrage or shame?
And you could just resign and tell us later if it was outrage or shame, if announcing it now would compromise an ongoing investigation.