Robert Dreyfuss reports that, according to former Iranian Foreign Minister Ibrahim Yazdi, it really was rigged:

A coup d'etat? They've already made one! They've created a dictatorship, in fact. Do you know that last night the security forces occupied the offices of many newspapers, to make sure that their reporting on the election was favorable? They changed many headlines. They fixed the election.

The Guards are taking over everything, including many economic institutions. The ministry of the interior is increasing its control in all the provinces.

We have information that Ahmadinejad is thinking about changing the Constitution to allow the president to serve more than two terms, to make his presidency more or less permanent.

The revolution is being twittered.