I speculated a few minutes ago that the momentum might be shifting in Iran. Josh Marshall is thinking along the same lines:
On the face of it, Khamenei could call for a review and then decide that it all checks out and that’s the end of it. But it’s my experience that that’s not how these things play out. When regimes ride these crises out successfully they almost always do so with a united phalanx. You simply do not grant the premise of the critics. Force, much as we like to think otherwise, is often quite effective. (See Tiananmen Square.) Once you do, once you legitimize the premise of the protests, which can quickly shift the momentum of the drama, it’s a very slippery slope for the regime.
As Josh emphasizes in his full post, the next 24 hours are crucial. Ahmadinejad has already delayed a visit to Russia—another sign that he might be vulnerable.