Nightmare Scenario II
In Iraq, everybody knows Nightmare Scenario I. That's where our invasion gets bogged down on the way to Baghdad, the fight moves into the city, the Kurds and the Turks go after each other full scale, the poison gas comes out, and Saddam may or may not have escaped into Iraq's western desert. When the fight is officially over, everybody starts taking potshots at US troops while every Islamist nutcase in the world shows up and starts trying to build his own little Taliban. Iran starts doing "border adjustments.", North Korea builds toward a temper tantrum, China starts making noises about Taiwan, and India and Pakistan face off again.
This is the "obvious" nightmare. How likely this scanario (or any part of it) is is a matter for discussion, but it's in everybody's mind (except, possibly Georgie Bush's).
What could be worse?
How about this? We get ready to roll. We start up the major bombardment that our troops won't move without. And we get a radio message from Baghdad that Saddam is dead. His generals offer us his head (literally!). Aziz goes to the UN and says "all over" and asks for UN protection from a US invasion.
Our whole rationale for this little expedition is that Saddam Hussein is Not A Nice Man. Everything is His Fault. Now he's gone, and so is our rationale for being there. Do we just go home?
And the Ba'athists are still in power (think Nazi with "Aryan" replaced by "Arab"). Weapons of Mass Destruction? Nope. Not us. Democracy? Not likely. Inspectors? Why?
We've accomplished essentially nothing. Saddam's successor, lacking Saddam's charm and abilities, will almost certainly be a worse thug than Saddam himself. Dictators make sure that anybody with real talent or leadership dies suddenly. Then they get to yell "Why am I surrounded by idiots?" a lot. We've burned an incredible amount of international goodwill. The French and Germans are going to remember a lot of the more unfortunate things that have been said about them. Do we really want them building their own high-tech armies, and maybe inviting the Russians in on the deal? We may have damaged the UN irreparably (hold the cheering from the John Birch Society), and turned it into the "alliance of everybody but the US". Rember the Law of Bar Fights -- you may be able to whip anybody, but you can't whip everybody. Domestically, we've seen 'way too many people yelling "treason". Georgie Bush's comment regarding Mexico's opposition to the UN war resolution "I don't expect for there to be significant retribution from the government" was especially unfortunate.
True, we have these results whatever happens. But if we get what we want out of the war, it won't all be for nothing. Worth it? Personally, I think that, at this point, there's no way we can ever get anything like a reasonable "return on investment" on this one.
Moral -- there's more than one way to lose a war.