Almost anywhere you look today, you can find references to "Bush's worst week", etc. The Libby indictment, the Miers fiasco and the fact that the 2000th military fatality was recorded in Iraq this week do add up to a pretty bad week, but I don't think this was the President's worst week by a long shot. That was the week following Hurricane Katrina.
Almost nobody in America knows who Scooter Libby is and if he remains as the sole indictee, then the political damage to the White House will be minimal. The Miers nomination was a "mistake" because it undermined Bush's support with his base, many of whom have spent 3 decades working for this one moment: Republican President and Republican majority in the Senate. However, a Machiavellian reading of the Miers nomination was that she volunteered to be publicly skewered (nominated and, predictably, investigated and attacked) so that Bush could "give in" to his base at exactly the moment that Fitzgerald was about to deliver his report. And, although 2000 is something of a milestone, I'm not sure it's politically much more significant than 1950 or 1900 or 2050 or 2100. If you believe in the war, then each death is tragic, but hardly politically earth-shattering. And, if you don't believe in the war, then each death is one too many.
No, in fact, I think Bush's worst moment was that week after Katrina and this week actually provides some solid footing for Bush to begin rebuilding the momentum.