There are likely negative consequences to this:
- Security means increased checkpoints and house searches. These will exceedingly unpopular with the Iraqis.
- This frustration is going to be transfered to the Iraqi government, which will be seen as giving away national sovereignity. The government's standing will be eroded.
- The U.S. will have to choose a Shiite faction to back -- the SCIRI or the Madhi Army. They will choose the Iranian-backed SCIRI, deepening the schism within the Shia and making it more difficult to put the country back together again.
- The Mahdi Army will be a new and troublesome foe to U.S. forces.
- U.S. casualties will shoot up. In order to hold neighborhoods U.S. forces will be far more exposed than they were before. This will further erode political support for the war in the U.S.
- U.S. military force will be stretched close to a breaking point; our flexibility to respond to other threats will be diminished.
By the end of 2007, fearing the annihilation of their party at the 2008 polls, a group of moderate Republicans will enter the Oval Office and threaten to revoke funding for the war. Given that political cover, Democrats will be willing to vote with them. That's probably what it will take to change Bush's direction in this war.