I don't doubt that Saddam has a loyal following among his minority Sheite (sp?) sect. If they happen to lose power, which they will in a war, then the Kurds and other sects repressed under Saddam will seek revenge.
If they do dig in and defend Bagdad with over 5 million people then significant civilian casualties will be inevitable and I would think significant casualties on our side as well.
William Hung is to American Idol as Sarah Palin is to the Vice Presidency