Enduring America has an interesting analysis of yesterday’s events. Here’s a key part:

By the afternoon, Rafsanjani’s office was being less subtle. Mehdi Hashemi continued to declare his innocence and then turned “corruption” against Ahmadinejad, declaring that the President, as Mayor of Tehran, had “lost” millions of dollars. More importantly, I suspect, the Rafsanjani camp took the fight to Ahmadinejad’s ally and Chief of Staff, Esfandiar Rahim-Mashai, attacking his “hallucinations” and calling on both Rahim-Mashai and Ahmadinejad to back up their criticisms of Rafsanjani in court.
And then last night came the dramatic challenge to the President, from a most unexpected challenger. We had wondered on Tuesday whether the Supreme Leader was behind the fourth trial, especially given the attacks on Rafsanjani. In a speech to student leaders, he gave the answer: the opposition had not been engaged in a foreign-directed “velvet revolution” against Iran. For anyone thinking of more arrests, including leaders like Mousavi and Karroubi (and, less likely but still possible, for those throwing around spurious indictments in trials), “We should not proceed in dealing with those behind the protests based on rumours and guesswork. The judiciary should only give rulings based on solid evidence, not on circumstantial evidence.”
A three-word summary. Back. Off. Mahmoud.