And I'm saying that you don't understand how Iranian politics work. The President is a bright shiny thing used to distract from the seat of real power, which is the clerics as embodied by the Supreme Ruler. Mousavi, by the nature of their political system, is already beholden to the clerics for whatever minor changes he can propose.
This is the opposite of modern England: it doesn't matter who the King or Queen is. The real power lies with the Prime Minister's office. In Iran, it doesn't matter who the president is. The real power lies with the Supreme Leader's office. The Wikipedia article is actually pretty good on the subject:
Politics of Iran - Wikipedia, the free encyclopedia
Any debate over this election is really about who is going to be the mouthpiece for their anti-Americanism, which is a cornerstone of their Revolution. The message will stay the same since it, by necessity has to, but there will only be a variation in its tenor. If you think that Khatami was less anti-American, I invite you to look at his actual record. The main differences between them are almost solely internal policies, such as freedom of expression and tolerance of non-Jewish minorities. In terms of foreign policy, there has been little change in the message, just difference in the fevror Ahmadinejad brings with him.
And the message is set by the Supreme Leader and the Council of Guardians. They are the de facto rulers of the country.