The concerns of the Sunni about the new constitution appear to be valid. One of the things the Sunni do not want is for the Kurds or the Shi'ites to monopolize oil revenues in the future. Currently, the plan is for oil revenues to be split based on current oil wells. Revenue from future oil wells would go to the particular region where the well is, however. Considering that the vast majority of Iraqi oil has not been drilled for yet, this would lead to a situation where the Sunnis are guaranteed to be cut out of most future oil income.
Meanwhile, the cold war between the major Shi'ite paramilitary groups has just heated up, and now Moqtada al-Sadr appears to be threatening to pull his support from the government. The fracas, which started with an attack on Sadr's followers in Najaf, has apparently spread, both in Baghdad, where the Badr Brigade HQ was attacked by Sadr supporters, and in Basra, where two missiles were fired at SCIRI headquarters, presumably by one of Sadr's supporters.
If the paramilitary groups declare open hunting, this could also throw a monkey wrench into approval of the Iraqi constitution... it could even lead to Sadr actively getting involved in the fighting again, possibly forming a common cause with the Sunni.
But that's okay because Donald Rumsfeld was just saying the other day that there won't be an Iraqi civil war, no matter how many dead bodies get pulled out of the river in Baghdad.
"I haven't seen anything to indicate that the risk is greater today than it was yesterday or the day before."
You don't *see* anything?! Pull your head out of your ass, Rummy!