Mashaei promotes a nationalist, "Iran first" ideology rather than the cleric's "Islam first" dogma, and advocates a religious and political view that marginalizes the clergy. Both ideas are popular with Iran's middle class, further making him a threat, Ghaemi said.
The rift has taken on an increasingly spiritual element. Last month Ahmadinejad loyalists began circulating a DVD documentary anticipating the imminent return of the Hidden Imam Mahdi, a religious event comparable to the way Christians anticipate the second coming of Christ.
While belief in the Mahdi's return is central to Shiite Islam, the Iranian clerical establishment has never predicted a specific time of his arrival.
Ahmadinejad often speaks of the Mahdi's return and his followers note that the president, a man of medium build with black hair and a beard, resembles the mythical leader.
Ahmadinejad has played up and played into his follower's metaphysical religious zeal. Referring to his "halo of light" moment at the U.N., Ahmadinejad says on a widely circulated video in 2005, "I felt the atmosphere changed. All leaders in audience didn't blink for 27, 28 minutes. I'm not exaggerating when I'm saying they didn't blink. Everybody had been astonished ... they had opened their eyes and ears to see what is the message from the Islamic Republic."