The Bush admin made lots of noises about Iran, and the need for regime change around the time of the Iranian election in the summer of 2005 (LINK), essentially sinking any moderate hopes for victory.  All the rhetoric from the American government was a gift to Ahmadinejad.  And I suspect it was a deliberate attempt to get someone in office who they knew would be more radical and more extreme in his statements, thus making it easier to paint Iran as the next Islamofascist stae we needed to take down.