I believe John Edwards is delivering a speech on Iran and "the lessons of Iraq" right now. I only have some excerpts from the speech, so I can't fully evaluate it, but this seems like an important point:

But there is a difference between doing everything in our power to keep America safe and a reckless, belligerent policy that actually makes us less safe. The preventive war doctrine was a stunning departure from the policy that had kept America safe during both world wars and during the Cold War. It is wrong on the merits, wrong on the morals, and wrong for America.

Good for Edwards. I've found it infuriating how little the leading Democrats seem inclined to engage with the key strategic elements of Bush's response to 9/11 and this is the biggest nail that needs hammering down. Bush replaced decades of non-proliferation policy, to say nothing of centuries of good sense and basic morality, to decide that unilateral preventive military action should be at the center of our approach to dealing with the world. This is nonsense. The United States has long got along fine without waging such wars, and our effort to wage one has been a disaster. And yet somehow Bush has managed to recenter the American political debate so that an idea that would have seemed shocking ten years ago -- waging aggressive unilateral warfare against countries that haven't attacked us or anyone else -- is now meekly accepted by all as a vital part of the toolkit.

Again, good for Edwards.