Partly inspired by recent events in Iran.
With a PoD no earlier than 1978, find a way for Iran to come under the rule of the Mojahaden-e-Khalq (People's Mojahaden Organization of Iran), a radical Islamic Marxist organization that has long sought to overthrow the Iranian government and replace it with their own rule.
One way might be to somehow curtail the effectiveness of the Islamic revolutionaries early on. Perhaps, as in James G's Soviet Domination, Khomenei gets popped in the early days of the revolution and leftist groups are able to more effectively rally public support. Or perhaps you could have them become part of a government led by another Iranian communist group (Tudeh, for example) and eventually consolidate power.
Once we are able to establish a way for the MEK to rule Iran, how would an MEK-ruled Iran actually look like?If the group's current state is any indication, I would expect MEKIran to be something like a Middle Eastern North Korea. The MEK are known for demonstrating "cult-like behavior", having formed an effective cult of personality around it's leaders. Thanks to both ideology and geography, the MEK would likely become a Soviet ally. The US, the Gulf Monarchies, and Iraq would all likely view this state as a major threat.