The point you apparently missed
"A HUNDRED thousand Iraqis across the country marched yesterday in support of a maverick Shiite cleric opposed to a draft constitution..."
And this is a Shiite group...the Shiites are supposedly in favor of the draft Constitution. By themselves they are not particularly powerful. But if even one percent of those hundred thousand Iraqis choose to take their dissatisfaction to violence, that's a thousand potential suicide bombers. Keep in mind we haven't begun to talk about the numbers of disaffected Sunnis who may be prone to violence.
What we have here is a recipe for civil war in a nation with virtually no cultural tradition for peaceful democratic debate. This is why Mr. Bush's naive dream of imposing our notion of democracy on the Iraqis will require our long term occcupation of that country at a cost of thousands of American soldiers lives and hundreds of billions of AMerican taxdollars.
