The Tipping Point.(Jalaluddin Taheri )

For 30 years, Ayatollah Jalaluddin Taheri delivered sermons to the faithful from the shimmering blue-tiled Friday mosque in Isfahan, Iran. On July 8 he delivered a different message--his resignation. In a bitter letter, which was printed in reformist newspapers, Taheri, 76, denounced Iran's hard-liners as corrupt and repressive, claiming, "Those in power are using the people's beliefs and religion to reach their own materialistic aims." He also attacked conservative vigilantes, thought to be linked to conservatives in government, labeling them "louts and fascists... whose umbilical cord is connected to the center of power."

Taheri's act of protest, unprecedented in the 23-year history of the Islamic Republic, was a clear sign that there are divisions among Iran's ruling clergy. It was even more damaging because Taheri is a respected Islamic scholar, devoted revolutionary and friend of the late Ayatollah Ruhollah Khomeini. "Taheri's resignation was a bombshell," says a Tehran-based Western diplomat. "It was one of the biggest death knells for the hard-line regime."

Iranian media were initially forbidden to discuss Taheri. But in a society under incredible strain--torn between the hard-line regime and its young, frustrated population--his voice and those of other moderate clerics will resound loudly next year; they pose a bigger threat to the regime than any other single group in Iran. And Taheri is not keeping quiet. His views continue to show up in reformist publications. In early December, he criticized the judiciary for their sentencing of Hashem Aghajari, a reformist history professor slated to hang for saying Muslims shouldn't follow their religious leaders "blindly." Students have already made an attempt to join forces with the cleric. He was asked to speak at a protest rally held by ...