Max Sawicky, still fretting about the future of the nation, laments that during the election "On the war, the argument was basically there were no WMDs so the invasion was unjustified. In other words, if there were WMDs, it would have been. Might have been, with a 'competent' Administration." Everyone knows where I stand on the competence issue. The WMD one, is, I think, interesting and complicated. In particular, one of the paradoxes of the Iraq War is that though it was sold with reference to an advanced Iraqi nuclear program, had there actually been both an advanced Iraqi nuclear program and a US administration genuinely concerned about it, there almost certainly wouldn't have been a war.
After all, if there had been an advanced nuclear program, the IAEA inspectors would have found it. Having found it, they would have destroyed it. Having destroyed it, destroying Saddam's WMD program hardly would have served as a casus belli, particularly for an administration that that was worried about nukes in a good-faith way rather than deploying them as a bad-faith scare story.
Long story short, it's not incredibly clear what scenario the counterfactual is specifying here.
One possibility is that there is a nuclear program, the IAEA finds evidence of it, but Saddam straightforwardly refuses to disarm -- perhaps ejecting the inspectors again. Had that happened, there would have been war. But it would have been a very different war. It would, for example, have secured Security Council authorization and the military coalition would have included at least token contributions from a wide range of countries. It would, what's more, have had much more limited goals -- creation of some kind of stable, nuke-free regime -- none of these grand ambitions to remake Iraqi society or transform the geopolitics of the region. I think that might have more-or-less worked. What's more, though I know the more serious anti-interventionists of the world will disagree with me, I also think you'd have to call a duly authorized war designed to enforce bona fide cease-fire terms of an earlier war that was, in turn, duly authorized by the UN in response to an Iraqi breach of the norm against conquering your neighbors a non-imperialist military venture.
Now, all that being said, I still think deciding that late 2002 and early 2003 was a good time to implement a big focus on Iraq would have been a policy error. There were much better things to be focusing on at the time, namely stabilizing Afghanistan, pursuing bona fide al-Qaeda terrorists, and trying to work to get the Israel-Palestine peace process rebooted.