(I posted this during the last presidential election, but I think this statement keeps getting more important the longer we are in Iraq...)
Trying to eliminate Saddam... would have incurred incalculable human and political costs. Apprehending him was probably impossible.... We would have been forced to occupy Baghdad and, in effect, rule Iraq.... there was no viable "exit strategy" we could see, violating another of our principles. Furthermore, we had been self-consciously trying to set a pattern for handling aggression in the post-Cold War world. Going in and occupying Iraq, thus unilaterally exceeding the United Nations' mandate, would have destroyed the precedent of international response to aggression that we hoped to establish. Had we gone the invasion route, the United States could conceivably still be an occupying power in a bitterly hostile land.
-- George Herbert Walker Bush, from his memoir, "A World Transformed" (1998)