Rafsanjani’s letter is especially significant because he leads the Assembly of Experts, an 86-member body of senior clerics that has the power to remove the supreme leader, Abtahi said. It included a veiled threat: Rafsanjani implicitly compared Ahmadinejad to a former President whom Rafsanjani helped depose in 1981.

In this year’s campaign, Moussavi, a former Prime Minister with a reputation for honesty and competence, has emerged as Ahmadinejad’s strongest challenger.

Moussavi and others have derided the President’s efforts to associate them with Rafsanjani. But Rafsanjani’s family is playing a powerful role in supporting Moussavi’s campaign — whether by invitation or not.

Rafsanjani’s 39-year-old son, Mehdi Hashemi Rafsanjani, directs the sophisticated electoral effort based at Islamic Azad University, which was founded by his father. It is here that the young women, paid $20 to $25 a day, can be seen at all hours assembling data to help election monitors observe the vote on Friday.