The three most powerful forces in the modern world are democracy, religion and nationalism. In 1989 in Eastern Europe, all three were arrayed against the ruling regimes. Citizens hated their governments because they deprived people of liberty and political participation. Believers despised communists because they were atheistic, banning religion in countries where faith was deeply cherished. And people rejected their regimes because they saw them as imposed from the outside by a much-disliked imperial power, the Soviet Union…

There is one way religion could be used against Iran’s leaders, but it would involve an unlikely scenario: Were Grand Ayatollah Ali Sistani to issue a fatwa condemning Tehran from his base in Najaf, Iraq, it would be a seismic event, probably resulting in the regime’s collapse. Remember, Sistani is Iranian, probably more revered in the entire Shiite world than any other ayatollah, and he is opposed to the basic doctrine of velayat-e faqih — rule by a spiritual leader — that created the Islamic Republic of Iran. His own view is that clerics should not be involved in politics, which is why he has steered clear of any such role in Iraq. But he is unlikely to publicly criticize the Iranian regime (though he did refuse to see Ahmadinejad when the latter visited Iraq in March 2008).