Daniel Larison, among others, has been right to point out that however inspiring the Iran protests have been, Mousavi is no liberal lion:
Compared to the differences between Obama and Bush on foreign policy, which are few but real enough, Ahmadinejad and Mousavi are even closer together. Before the election, someone called Mousavi Iran’s Kerry, which was a bit of an insult to Kerry, because by 2004 even Kerry was farther away from Bush on foreign policy than Mousavi is from Ahmadinejad today.
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If we focus on the individual leaders to find some indication of changes in policy, we are fooling ourselves. In the best-case scenario, Mousavi is a rallying point around and a vehicle through which an entirely different kind of political force can organize.
The analogous American situation is that of Howard Dean, who went from establishment to grassroots with surprising speed. A Yale graduate and governor of Vermont whose ancestors had close relationships to the Bushes, Dean was a political centrist who signed the Vermont bill legalizing civil unions behind closed doors because he eschewed confrontational politics. This cautious patrician–more G. H. W. Bush than Michael Moore–was transformed when the netroots rallied around him. A consummate insider and centrist became a symbol of the radical and disenfranchised.
When a politician sees a mass uprising misunderstand their positions, they are sometimes likely to actually change their positions to be more in line with what will please the crowd. When Dean experienced a surge in popular support, he really did move to the left. Obviously, the room for political movement in Iran is much narrower. But suppose that the people really did rise up en masse and demand constitutional change in the Iranian regime. Would Mousavi really refuse to adopt substantive reformist positions if those positions appeared to be his ticket to power instead of (as they now must seem) political suicide?