The Turnout And The Margin

This is Nate Silver-bait. But an Iranian-American reader asks a good question. Under what circumstances with a turnout of 85 percent do landslides for incumbents happen, as the regime claims in Iran? Are there any precedents for this in electoral history? One way of tackling the question of fraud is simply probability. How many election results in history have never varied from region to region or from the beginning of the count to the end? Does this result have any serious precedents? Or is it as self-evidently rigged as it increasingly seems?