Who might succeed in Iran's theocratic system of power?

The killing of Iran's Supreme Leader Ayatollah Ali Khamenei in US and Israeli strikes throws the survival of the country's theocratic system into jeopardy and it is hard to predict who might succeed him or what will happen next.

Strikes are still targeting the ayatollahs, Revolutionary Guardsmen and veteran advisers to Khamenei who have run the country for decades, while an interim committee mandated by the constitution has temporarily taken over the leader's duties.

The following explains how power is meant to operate in the Islamic Republic, how a new supreme leader could be chosen if the system survives, some of the possible candidates, and how the US and Israeli attack may have changed the equation:

What is Iran's 'supreme leader'?

Iran's theocratic system dates to the 1979 revolution that ousted the Shah. Ayatollah Ruhollah Khomeini, the leader of the revolution, introduced a new system of rule: vilayat-e faqih, or guardianship of the Islamic jurist.

The theory holds that until the return of the Shi'ite Muslim 12th Imam, who disappeared in the ninth century, power on earth should be wielded by a venerable cleric.

It means whoever takes over as supreme leader, empowered by the constitution as the ultimate authority guiding the elected president and parliament, will have to be a senior cleric.

Under Khomeini, who died in 1989, and Khamenei, who has ruled since then, the supreme leader has had the last say in all matters of state. But any new leader would have to assert his authority at a moment of enormous rupture.

Who will choose Khamenei's successor?

The constitution says a new leader must be chosen within three months. Until then President Masoud Pezeshkian, Guardians Council member Ayatollah Alireza Arafi and Judiciary chief Ayatollah Gholamhossein Mohseni-Ejei will take charge as a temporary leadership council.

Choosing a new leader is meant to be the responsibility of the Assembly of Experts, a body of around 90 senior clerics who are elected every eight years, though with strikes continuing it is not clear how or when they will be able to meet.

Khamenei never publicly named a preferred successor and in practice the decision will likely be made by the most senior figures in the Islamic Republic who have wielded power under Khamenei for many years. The recommended successor would then have to be approved by the assembly.

The most important of those senior figures is Khamenei's veteran adviser Ali Larijani, widely seen as Iran's foremost powerbroker.

Who are the main candidates?

Khamenei's son, Mojtaba Khamenei, has at times been seen as a likely successor but his fate is unclear. His wife was confirmed killed in a strike in Iraq on Saturday and there has been no certain news as to whether he died too.

That may mean Khomeini's grandson, Hassan Khomeini, is a more likely choice. Khomeini is closely associated with the reformist faction that has for decades tried to moderate the Islamic Republic's stance and may be seen as better able to assuage Western enmity and calm the fury of an embittered population

Arafi and Mohseni-Ejei are less prominent possibilities who would likely continue Khamenei's hardline stance. Mohseni-Ejei was responsible for stamping out internal protests following a disputed election outcome in 2009 when he was intelligence minister.

Assembly of Experts members Ahmad Alamolhoda and Mohsen Araki are also hardline senior clerics with a close involvement in Iranian politics who might be considered. Former president Hassan Rouhani is a senior cleric but he was distrusted by some of the most powerful hardliners who would have great sway over the choice.

The assembly could theoretically pick an even less known ayatollah as leader. But the ruling system has been so fractured by the strikes that it would be much harder to buttress the position of a newcomer.

What role will the Revolutionary Guards play?

The Islamic Revolutionary Guards Corps had long been expected to play a central role behind the scenes in determining Khamenei's successor. Unlike the ordinary military, which comes under the elected president, the guards answer only to the supreme leader.

But its top echelons have been hollowed out by US and Israeli strikes over recent years and it is far from clear how far it will still be able to influence the decision.

The most important Guards leader of recent times was Qassem Soleimani, head of the elite Quds Force unit that spearheaded Iran's regional strategy of exporting the revolution through affiliated Shi'ite militias in Arab countries. He was killed by a US strike in 2020.

During the brief summer war last year Israeli strikes killed other top Guards commanders. And Saturday's strikes killed its latest top commander Mohammed Pakpour, three sources familiar with the matter said.

The Basij militia, a part-time paramilitary force under Guards control, is often used to quell protests inside Iran, giving the corps a formidable role in internal control.

Since the early 2000s, the Guards' economic power has also grown as its contracting company Khatam al-Anbiya won projects worth billions of dollars in Iran's oil and gas sector. Protecting that empire may contribute to the Guards' decision on backing a new leader.

Will Iran's people get a say?

Iranians elect a president and a parliament to four-year terms. The president appoints a government that handles daily policy within parameters permitted by the supreme leader.

During the early years of the Islamic Republic the votes drew mass participation. But far fewer Iranians retain faith in electoral politics.

While President Pezeshkian, a reputed moderate, is on the three-member interim leadership committee, it is far from clear he will have much say over how events pan out.

And while the Assembly of Experts is elected, all its candidates - like those running in all Iranian national elections - must be vetted by the clerical Guardians Council, meaning only those already aligned with the authorities can take part.