In the western imagination, Iran is a dictatorial - even totalitarian - state. This analysis may not reflect the country's highly complex political dynamic, but there is little doubt that over the past few years Iran has suffered from an "authoritarian lurch". Increasingly, power is centralised in the office of the Supreme Leader, occupied since 1989 by Ayatollah Ali Khamenei, successor to Ayatollah Ruhollah Khomeini, leader of the 1979 Islamic revolution.
Khamenei's elevation to high office, reportedly following a deathbed nomination by Khomeini, was greeted with some surprise by other clerics. Khamenei was not at the time a senior ayatollah, and was not thought to be of sufficient theological standing. While Khamenei has sought to balance Iran's rival factions, he has tended to side with the conservatives and his repeated interventions in the political process have drawn considerable criticism from reformist politicians. Conservatives, on the other hand, view him as too indecisive.
According to its 1979 constitution, Iran is an "Islamic republic" that combines the democratic features of republicanism - an elected executive and legislature - with the ethical framework of Islam. This framework is overseen by the Supreme Leader. Despite the democratic advances of Mohammad Khatami's presidency (1997-2005), in recent years Khamenei has become increasingly authoritarian, a trend supported by hardline conservative control of the judiciary and legislative vetting body, and heavy manipulation of the election process. With its democratic credentials in doubt, the current government, led by Mahmoud Ahmadinejad, has resorted to populist tactics. But the authoritarian lurch is far from complete - despite Khamenei's wide-ranging powers, Iranian politics is best characterised as personal and arbitrary, rather than totalitarian.
Ali M Ansari is reader in modern history at the University of St Andrews