Tunisian and Egypt vs Iran

With the success of the protesters in Tunisia, and what seems to be the eventual success of protesters in Egypt, what was different about the protests in Iran that kept the Iranian protesters from being successful?

In answering that question on the news the other day, it was pointed out that Tunisia and Egypt both have/had one sole dictator/figurehead running the country. Despite what we might think, Iran actually has a government and their leader is less of an absolute authority and answers to his political party. At least that was the comment on the news that I heard.

The Iranian government, however much its in internal position may be eroding ( and there is a great deal of speculation on the topic ), still has a sizeable native constituency. It’s primary adversaries have traditionally been found among the secular, professional middle-class ( now perhaps spreading to some of the urban working poor ). Meanwhile it has tended to hold the loyalty of the rural and some segments of the urban poor, as well as the Bazaari class, primarily religiously observant lower-middle and middle class shopkeepers.

Tunisia and Egypt are plutocratic kleptocracies and oddly enough ( or not ) have been considerably less democratic than the Iranian theocracy ( at least until recently, depending how you view the recent Iranian election ). They really are rather more precariously perched regimes to begin with, with relatively small natural constituencies. Ahmadinejad and Khamenei have plenty of genuine, enthusiastic supporters in addition to the security apparatus. Ben Ali and Mubarak mostly just had/have the latter.

If the Egyptian protesters are successful and other middle-eastern countries such as Syria have successful revolutions, I wonder that will encourage unhappy Iranian protesters to try again.