In the debate concerning authorizing the war, one of Bush's main points is that Kerry saw the same intelligence, everyone saw the same intelligence. But there is something in this argument that seems to be forgotten.
They used to say it (years ago) that intelligence is never 100%. Depending on language, what kind of spies we're able to get in, other technology, etc., the intelligence can be 90%, 80%, varying degrees of correct. But Bush presents the intelligence argument as though it's 100% or nothing and I don't see anyone challenging him.
The way to attack the Administration on this is to point out that they didn't see any shades of grey, they didn't level with the American people, saying 'we're not absolutely certain about WMD or anything else but we're going to war anyway.' Nuance is good when it gets you closer to the truth, the sledge hammer approach is bad when it gets you into unnecessary wars.