We'll probably never know...

... if Ahmadinejad really did win the Iranian presidential election by a landslide.
He might have.
Or - the result could be based solely on fraud.

As stated: we'll likely never know.

The current Iranian regime might want to consider, however, that it was widespread public disenchantment with the Shah & his thuggish security forces that brought them to power.
Yes - it is possible for popular revolutions to succeed against well-armed police states, even in the modern era.