Something about this war is eating Bush's detractors alive, something unquantifiable with conventional weights and measures. I think that it is because if George W. Bush really did lie (and thus surprising both the Right and Left), the anti-war crowd would still have to face a disheartening Spectacle of Freedom For An Entire People, instead of the more satisfactory Humiliation Of Bush At The United Nations And Mass Graves Nobody Knows About.
Nothing is more irritating than watching your enemies fail to live up to your worst expectations. If George W. was hawking stolen museum art, or John Ashcroft was forcing Shiites to convert, or Dick Cheney was sucking the oil from Iraqi teenager's skin, the Left would have far lower blood pressure. They would be relieved, vindicated, because the war would be delightfully immoral.
The anti-war crowd long ago started measuring themselves as culturally, intellectually, and morally superior to the pro-war crowd, instead of measuring whether their policies were superior. Thus, the incredible success in Afghanistan and Iraq is not a blow to their policy, it is a blow to their ego and sense of self.