A carefully planned theft of the election would at least have conceded Tabriz to Moussavi and the rural western Iranian villages to Karoubi.
As the kids would say, OMG! Ahmadinejad may have more caused more trouble than he needed. The worst outcome he faced was a runoff--no need to butcher the results so badly. Either tweak them or let them play out as long as runoff or a win seems likely. Only if an expected first round majority for the opponent would have made something like this worthwhile. However, as I find in my classes, those who cheat do so because they haven't figured out how to succeed the ordinary way--that they are not so bright. Hmmm.