For all the talk about the success of the “surge” in tamping down violence in Iraq, surely Moqtada al-Sadr’s decision to declare a 6-month ceasefire and shut down the Mahdi Army is a big reason why we’re seeing relative calm in Baghdad and beyond.

But Sadr’s followers are running out of patience:

“There is an entity in the Sadr trend that doesn’t want the freeze,” said Sheik Naza al Timini, a Sadr cleric in the Shiite holy city of Karbala, south of Baghdad. “They said, ‘We have the right to use violence and force.’ We always hope for good, and we hope that the decision of Sayed Muqtada will be for the best of Iraq, but after he gives his final decision about the future of the Mahdi Army, many, I believe, will change their ideology and choose to leave the Sadr trend.”

Sadr’s proven remarkably deft at playing this game. If he sees a reason to extend the cease-fire, he will. But keeping the more radical elements in line may prove elusive. It’s a problem common to any insurgent group, from the PLO to the IRA. When the established leadership starts cutting deals with the perceived occupiers, a more violent splinter group usually emerges, gains credibility, and pillories the old guard as weak-kneed. Sadr’s strident anti-Americanism seems to be part of his effort to avoid this fate.