Sooner or later the Saudi regime will fall. When that happens, would the US be in a better position with a friendly Iraq, or a militant Saddam's Iraq, that aligned with Syria, Iran, and Wahhabi/AQ SA would surround tiny Kuwait and Bahrain? Not to mention the oil situation, the weak link in our economy....
One of the real problems for the Bush team is that so much of what makes the war justifiable can only be mentioned sotto voce. And sotto voce just doesn't work when an electorate has to be rallied.