Democracy in America goes back to pre-election profiles of Mir Hossein Mousavi and finds a "cautious, pragmatic, vague and increasingly shrewd politician." This seems a fair verdict and, as we know, Mousavi can hardly be the perfect poster-boy for liberals since, if he were, he wouldn't have been permitted to stand in the first place. But that was then and this is now. The movement is bigger than Mousavi now and it's hard to see how much of it he and his advisers really control anyway.
What can be said is that reform is a process, not an event. Furthermore, I would hazard that the regime faces a pretty bleak choice: manage change now or risk demands for reform in the future that you cannot manage, control or put out. That in turn would leave Iran's rulers to make a choice between engagement or a kind of Burmese-style brutality that would also bring a Burmese-style isolation. It's hard to see how that's in Iran's interests.
Of course, managing change is not easy. It can run away from you. Gorbachev never intended, I think, to preside over the demise of the Soviet Union. (It's worth noting that some of the people who objected to Reagan even meeting Gorbachev are some of the same people who simultaneously dismiss the possibility of reform in Iran while also urging Obama to intervene in ways that would frustrate, not advance, the case for change.)
But since analogies are all the rage these days, here's another one: might Mousavi be a kind of Iranian FW de Klerk? There's no certainty, of course, that he - or someone like him in the future - will be, but nor, I think, should one discount the possibility that he could be. de Klerk, after all, had served for years in PW Bothas government without showing any interest in reforming, let alone ending, apartheid. Nor did he have anything other than a conservative reputation when he running the National Party in the Transvaal.
Yet by the time he came to power in 1989 de Klerk had come to appreciate that matters couldn't carry on like this forever. Something had to give. But he wanted it to give gradually, not overnight. Even then, matters moved more quickly than was comfortable for the old regime and, though notionally in charge, de Klerk was also at the mercy of events.
The parallels are not, as always in these affairs, exact. For one thing de Klerk established a degree of international goodwill by winding up South Africa's nuclear programme; it seems unlikely that any Iranian leader will be quite so accomodating. Nonetheless, Mousavi, or someone else, may find themselves in the de Klerk position: knowing that the game is up but playing on in the hope that total meltdown can be avoided.
The alternative, as I say, is for the regime to double-down on the opposition. But while that may win it a temporary respite domestically, it seems likely to store up more and greater danger that will eventually have to find an outlet. In other words, the regime now has an interest in managing change too. And once the process of change begins, it's foolish to predict too confidently where it might end. Granted, this is a powerful incentive for the regime to frustrate change but, as I say, that seems like playing for time rather than a solution in and of itself...