"The fundamenalists played a very muted role until the eve of the revolution and after when they managed to mobilise the population from the mosques against the secularists that I have mentioned."
This is half-true, and I don't think that it undermines Chuck's argument. Here's Parsa, "States, Ideologies, and Social Revolutions," p 145.:
"More significantly, because of their moderation [compared to the secular forces], the mosque retained some measure of immunity from the state, in part because it did not represent any serious threat to the government. As a result, mosques remained open and available as places for assemblies and religious ceremonies. Indeed, the mosque was the only institution with a national network that was relatively immune from the power of the state, and by the time of the revolution, it represented the only option available for mobilization....Yet, it should be emphasized that political mobiliztion did not begin in the mosque, nor did the clergy initiate it. The mosque became a center for mobilization only after intense repression stifled opposition protests elsewhere."
I'd add that the political outlook of the clergy was fairly heterogenous. Among the most popular, perhaps the most popular, was Ayatollah Taleghani, a former Mosaddegh supporter, an advocate of popular democray and workers' councils, and strongly opposed to a theocracy. He died after the revolution, "under mysterious circumstances," possibly killed by the Khomeini faction. Other more progressive clergy either fled the country, were imprisoned, or were killed by Khomeini. The initial heterogeneity of the clergy made it possible, for a time, for the clergy to appear capable of representing a broad range of positions, and this probably undercut the appeal of the secularists until it was too late. Randy