In hindsight, I'm not sure there was anything that could have kept this war from starting, given who is in power. Saddam wasn't built to step aside, and Bush wasn't built to believe disarmament was possible without regime change. Two very flawed men, both built for violence, taking a whole lot of unwilling people with them.
There are a lot of things, however, that could keep Bush from meeting his full objective. One thing I was thinking of today was what if Saddam staged a coup? Or his death? I mean, if Iraq convinced the world that the US had a lucky strike and killed all the leaders and that they surrendered and the war was over, it would be really tough for Bush to justify further bombing. There wouldn't be need to rebuild, and the Iraqis, given that there wouldn't yet be an occupation, would have the high ground in telling the US that it wasn't necessary for them to come in, they could rebuild their democracy by themselves. That would be really politically tough for the U.S. Then months later, surprise, Saddam is alive.
Meanwhile, we're days away from the US dropping ten times the amount of bombs on Iraq in a day than the heaviest day in the '91 war. I just can't get over the reality that lots of good people are going to die.