He's kind of hamstrung. It's Sadr who keeps him propped up.
But the Iraqi people (including the Shiites) are getting fed up with the militias, as are many high ranking members of the Iraqi Parliament, so something's going to have to give. The next couple of months should be interesting.
Thanks for your insight. He seems weak to me, but I also know that he is in a very difficult position. Do not envy the man.