Here are the most likely candidates to replace Iran's ailing Supreme Leader

Iran's Supreme Leader Ali Khamenei is reportedly dying.

The ayatollah, the final arbiter of all of Tehran's internal and external policies since 1989, is thought to have terminal cancer and his death could be imminent.

Once Khamenei dies, Iran will undergo an important political shift. Since the Islamic Revolution installed a clerical theocracy in 1979, the country has only had two supreme leaders, meaning there's only been a single power transition in 35 years. Khamenei has ruled as Iran's supreme leader since 1989 after the death of the first supreme leader, Ruhollah Khomeini.

After Khamenei's death, Iran's constitution stipulates that the next supreme leader is to be chosen by the Assembly of Experts, a body which hasn't been consulted in decades. The assembly, comprised of 86 elected religious leaders, would have the ultimate say in who will replace Khamenei.

So far, all signs point to the next supreme leader of Iran being just as much of a hardliner as the conservative Khamenei - if not more so. In an internal election, the Assembly of Experts elected conservative Ayatollah Mohammad Yazdi as the head of the political body on March 10. Meanwhile, Iran's Islamic Revolutionary Guards Corp (IRGC), a nationalistic and sectarian military force long patronized by Khamenei, is at the zenith of its political power in the country, Mehdi Khalaji, a senior fellow at The Washington Institute, writes for Politico.

There are a few plausible candidates, but none of them represents a major rupture with the current revolutionary clerical regime.

"It is difficult to prophesy the outcome of Iran's current power struggle," analyst Ali Alfoneh wrote in a policy brief for the Foundation for Defense of Democracies. "But given the likely candidates to lead the country, one scenario may be safely ruled out: that Khamenei's eventual demise will usher in a moderate Islamic Republic at peace with the world."

With that in mind, here are the most likely successors to Khamenei's rule.

Armin Rosen contributed to this report.