9:24 pm From BBC Persian:

Mohammad Khatami, former President of Iran, declared that the only way out of the current crisis is to rely on the will of the people and establish a referendum. He made this declaration in a meeting with a number of the families of people arrested in the election aftermath.
Mr Khatami organized this meeting at the office of the Association of Combatant Clerics with the presence of a number of important party members including Mohammad Mousavi Khoeiniha (Expediency Council member), Ali Akbar Mohtashami-Pur (midranking cleric), Majid Ansari (Expediency Council member, former VP of Iran), Mehdi Emami-Jamarani, and Mohammad Mousavi-Bajnavardi. In this meeting, Khatami welcomed the suggestions and opinions proffered by Ali Akbar Hashemi Rafsanjani in his Friday prayer sermon last week.
The Association of Combatant Clerics simultaneously produced their 5th announcement since the election, in which they emphasized the need for a referendum. They considered this the best solution according to the “exact text of the Constitution of Iran.”
The Association of Combatant Clerics’ message emphasized that “the trust of at least millions of people in relation to the electoral process has been lost,” and requested that “instead of insisting on unproductive alternatives that until now have produced nothing except bad results, organize a referendum in which the entire people can freely participate, in relation to the events that have happened, so it can serve as feedback [for the Islamic Republic].”
Mr. Khatami said that the referendum should be organized by a body like the Expediency Council (chaired by Rafsanjani).

This announcement signifies that the Mousavi camp and Rafsanjani have officially joined together in an attempt to force Khamenei to respond. Calling for a referendum is intelligent because it would allow the Supreme Leader to save face – as he would not necessarily be invalidating the election results.
It seems that Khamenei’s response to this development will depend on how much pressure he feels from the recent protests. And quite frankly, it’s a possibility that Khamenei does not possess the absolute power many believed him to have prior to the elections– perhaps the paramilitary will pressure him into continuing with his current policy.