To add a footnote to the Reza Aslan-Jon Stewart talk da Zombie has posted, I give you a little something concerning the position of the Supreme Leader, aka, the current Ayatollah, Khamenei, from Hooman Majd's The Ayatollah Begs To Differ. Boldface emphasis is mine:

Khomeini, as father of the revolution and someone who was elevated (some argue inappropriately) to Imam, an honorific that has seldom been applied to any Grand Ayatollah, as it implies sainthood of the sort that is the basis of Shia Islam with its twelve Imams, didn't need to worry about his authority and popular support while he was alive, but he was careful to ensure that his successors, who could not be guaranteed to enjoy the same privileges, would have an absolute authority that would entrench the Islamic Republic for generations to come. Today, the valih-eh-faqih, "Supreme Leader," is Ayatollah Ali Khamenei, the similarity of his name to his predecessor's entirely coincidental but guaranteed, as it has over the years, to confuse Westerners. He has, in the years since Khomeini's death elevated him to the post, carefully balanced his use of what is arguably unlimited power with the cultivation of a public perception that the elected presidents of the republic are responsible for the ordinary welfare and woes of the people, and their general dissatisfaction, if they have any, with their government. It's a difficult balancing act, one that he plays with enormous skill, for when the people are too happy, as they perhaps were in the wake of the initially extremely popular election of President Mohammad Khatami, he has to ensure that the credit for that happiness doesn't rest entirely with the elected officials; otherwise his very role might come into question. Similarly, a certain amount of dissatisfaction, whether from the left or the right, bodes well for his authority as Iran's "Guide," someone who can lead the nation through turbulent times. It speaks volumes about both Iranians' penchant for dislike of the leaders they elect and the Supreme Leader's deft manipulation of the political system that Iranians' disapproval of Khatami's inability to deliver on his promise of reform was blamed not on Khamenei directly, although Khatami and his allies implied as much at every opportunity and most Iranians understood the limits of the president's power, but on Khatami's unwillingness to stand up to conservatives and Khamenei, who by the very nature of his job supported the conservative agenda as often as, if not more often than, the president's. Blaming the weakness of their president rather than the strength of the Supreme Leader, then, stands in contrast to Khatami's successor's term, when those Iranians who quickly became unhappy with the state of affairs under President Ahmedinejad blamed him for incompetence and pigheadedness rather than Khamenei for his apparent inability or unmillingness to completely rein him in. The Supreme Leader, it seems, can never lose.

Khamenei's name has been cropping up more lately as he shows his hand in what started out as a dispute over a crooked election and has indeed turned into a bloody battle over the future of Iran's Islamic Republic. Let's hope something can be worked out between the people of Iran and the man behind their green curtain.