Speculation has again started swirling over the declining health of Iran's Supreme Leader, the Grand Ayatollah Ali Khamenei, with unconfirmed reports over the weekend that the 81-year-old had transferred power to his son, cleric Sayyid Mojtaba Hosseini Khamenei.

The wellbeing of Khamenei – who has held power since 1989 -- is in question. He was reported to have been diagnosed with prostate cancer around 2014 but those reports are shrouded behind a cloak of secrecy with the question of succession and its far-reaching domestic and global impact becoming increasingly important. Iran's Supreme Leader holds conclusive authority over all religious, political, and military matters in Iran.

So who is the younger Khamenei and just how influential has he been in pulling political strings inside the beleaguered nation?

For more than a decade, the 51-year-old cleric has seen as a potential successor to his father's throne. His increasingly dogmatic role overseeing numerous security and intelligence departments are viewed as part of the grooming process to ascend to the top spot, according to the Jerusalem Post.

In 2018, France’s Observatory on the Middle - East and North Africa offered some comments from the son that sounded not to dissimilar to the father. The group tweeted an interview with Mojtaba with Iraqi’s Al-Ayyam TV. The translation of the tweet: The representative of the Iranian Supreme Leader #Khamenei in Iraq Mojtaba Hosseini:#Israël this "cancerous tumor" will be eradicated in a few years.

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Born in the northeastern state of Mashhad in 1969, second eldest son and one of the Grand Ayatollah's six children, Mojtaba went on to study theology and then ventured to the holy city of Qom to become a cleric in 1999.

Mojtaba's life behind closed doors is also the subject of much secrecy. Reports indicate that he has been married to the daughter of the previous parliamentary speaker, Gholam-Ali Haddad-Adel, for at least 14 years. The couple – by most accounts -- leads a modest life with their two sons -- ages 13 and 3 --  and a 7-year-old daughter.

Two protesters burn the representation of the U.S. and Israeli flags as the others hold placards condemning inspections by the UN nuclear agency (IAEA) on Iran's nuclear activities and the country's nuclear talks with world powers during a gathering in front of Iranian Foreign Ministry on Saturday, Nov. 28, 2020 in Tehran. Supreme Leader Ayatollah Ali Khamenei is calling for “definitive punishment” of those behind killing of Mohsen Fakhrizadeh, the scientist linked to Tehran’s disbanded military nuclear program. (AP Photo/Vahid Salemi)

Two protesters burn the representation of the U.S. and Israeli flags as the others hold placards condemning inspections by the UN nuclear agency (IAEA) on Iran's nuclear activities and the country's nuclear talks with world powers during a gathering in front of Iranian Foreign Ministry on Saturday, Nov. 28, 2020 in Tehran. Supreme Leader Ayatollah Ali Khamenei is calling for “definitive punishment” of those behind killing of Mohsen Fakhrizadeh, the scientist linked to Tehran’s disbanded military nuclear program. (AP Photo/Vahid Salemi)

He has also been profiled as a mostly hardline, conservative figure – even more refractory than his father – with especially tight ties to the Iranian Revolutionary Guard Corps (IRGC).

"Due to the lack of transparency among those in power in Iran, nobody can say how much Mojtaba Khamenei currently influences Iran, but in recent years Khamenei's son has had a bolder role in Iran," Mojtaba Pourmohsen, a journalist at the London-based Iran International TV, told Fox News. "He has close relations with some prominent IRGC' Generals like Hossein Taeb, the head of Intelligence Organization of the IRGC, and with Hossein Nejat. He has a prominent role in the hidden economy in Iran. He has a role in determining the budget for organizations that belong to the Supreme Leader."

Nonetheless, the process of succession isn't quite as simple as the Ayatollah merely making a preference. Iran has constitutional laws with regards to the process of choosing the next-in-line.

In the aftermath of the 1979 Revolution, legislation was put in place that the Supreme Leader had to be someone who had reached the rare senior clerical position known as a "Major Mujtahid." This is a cleric who has amassed a number of judicial rulings in all components of life that have been embraced by the religious populous as "demonstrating ijtihad," encompassing expertise in Islamic law, worthy of others in the jurisprudence realm emulating.

However, the previous Supreme Leader Ruhollah Khomeini – reported not to have been fond of his small pool of possible heritors – loosened the reigns to allow someone with a less acclaimed pedigree in the legal field to be considered. That in itself enabled Khamenei to eventually take the reins.

Sarit Zehavi, CEO and Founder of Alma Research and Education Center, noted that reports on the change of leadership in Iran are speculative and likely originated in opposition sources. But added that Iran’s next leader technically should be a “Shura” -- an Arabic term, often for a council, which encourages Muslims to decide their affairs in consultation with those who will be affected by that decision.

"Due to the Shiite radical ideology of the Ayatollahs – the chosen leader should be the highest religious authority in the country," Zehavi explained. "Yet this was not the case after Khomeini's death – and that is why we can assess that after Khamenei's death, we will see internal battles inside the Ayatolla's regime."

In this photo released by the official website of the office of the Iranian Presidency, President Hassan Rouhani speaks in a cabinet meeting in Tehran, Iran, Wednesday, Dec. 2, 2020. Rouhani on Wednesday rejected a bill approved by parliament that would have suspended U.N. inspections and boosted uranium enrichment, saying it was "harmful" to diplomatic efforts aimed at restoring the 2015 nuclear deal and easing U.S. sanctions. (Iranian Presidency Office via AP)

In this photo released by the official website of the office of the Iranian Presidency, President Hassan Rouhani speaks in a cabinet meeting in Tehran, Iran, Wednesday, Dec. 2, 2020. Rouhani on Wednesday rejected a bill approved by parliament that would have suspended U.N. inspections and boosted uranium enrichment, saying it was "harmful" to diplomatic efforts aimed at restoring the 2015 nuclear deal and easing U.S. sanctions. (Iranian Presidency Office via AP)

And despite the rule-bending and Mojtaba's efforts to up his doctrinal prowess – having taken up a position teaching advanced religious courses at the prestigious Qom Seminary since 2009 after living among the Tehran elite for three decades – some analysts contend he still doesn't possess the pious chops.

But Iran's constitution also mandates that the permanent – rather than interim – successor be approved by the 88-ayatollah assemblage deemed the Assembly of Experts, should the standing Supreme Leader die or be rendered incapable of performing his duties.

The IRGC is also considered hugely influential in determining who takes the esteemed role, and debate has long simmered that the Assembly of Experts is a feeble, ceremonial institution beholden to the military's demands.

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In that regard, Mojtaba is believed to be well-entrenched. After graduating from a private religious high school in the nation's capital in 1987, he and his older brother served two years in the Armed Forces on the tail-end of the bloody Iran-Iraq war.

Norman Roule, a United Against a Nuclear Iran (UANI) Advisory Board member who served as National Intelligence Manager for Iran at the Office of the Director of National Intelligence (ODNI), said that since the successful cancer treatment, the Grand Ayatollah has appeared periodically in public looking considerably frail, spiking whispers of compiling health woes.

"This has given time for Iranian society to be very prepared for his death, but it has also given time for candidates (to prepare) to take his place," he conjectured.

Roule concurred that the Supreme Leader's son wields tremendous influence over the country's most harsh factions and has significant authority over the nation's finances and questions of corruption have subsequently surfaced.

But Mojtaba's shadowy influence on Iranian politics has been brought into the public limelight before, and his name steeped in controversy.

Mehdi Karroubi, the former speaker of the Iranian Parliament called the Majiles, wrote letters to Khamenei in both 2005 and 2008. Karroubi expressed frustration that Mojtaba had meddled in the Presidential elections – namely muzzling dissidents – with the aid of the IRGC and its affiliated Basij militia wing.

Following what many opponents viewed as a sham election in 2009, protestors took the streets with the slogan "Wish you death Mojtaba, so you would never be the next leader!" He is then reported to have instructed the militia to vehemently and violently cracking down on the criticism. 

Furthermore, the letters charged that Mojtaba had unethically "supported one of the candidates" – Mahmoud Ahmadinejad – who controversially retained the Presidency for a second term. The son's support is said to have influenced the top-ranking father to also shift his backing away from the more independent then Tehran Mayor Mohammad Bagher Ghalibaf to the staunchly right-wing Ahmadinejad. 

Ayatollah Khamenei responded with brusque words of his own, denouncing the accusations, and Karroubi was later put under house arrest for several days. 

In November 2019, Mojtaba was also slapped with U.S. sanctions by the Treasury's Office of Foreign Assets Control (OFAC), which seeks to "block funds from flowing to a shadow network of Ali Khamenei's military and foreign affairs advisors who have for decades oppressed the Iranian people, exported terrorism, and advanced destabilizing policies around the world."

Treasury depicted him as an official representative for the Supreme Leader "despite never being elected or appointed to a government position aside from work in the office of his father," and accentuated his links to the IRGC and the Basij militia.

But even with Mojtaba's deep connections to power on multiple fronts, policy observers anticipate that he will face stiff competition for the chief position among both stringent and reformer figures.

Another possible candidate is Hassan Khomeini, the 48-year-old grandson of the former Supreme Leader. In 2015, he declared his move from cleric to politician and attempted a run for the Assembly of Experts, a government body empowered to appoint and dismiss the Supreme Leader of Iran.

Khomeini’s bid was rebuffed by the Guardian Council, which vets assembly members, in a quest to demonstrate the murky line between religion and state affairs.

Roule also stressed that current President Hassan Rouhani could also be a potential candidate. While he has religious credentials, he lacks support from the hardline. From his purview, the Ayatollah has created an architecture to select someone "most like him," and the person who fits that bill is Ebrahim Raisi, the current Chief Justice of Iran also under U.S. sanctions.

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Red flags over Khamenei's health and the opaque and potentially problematic succession come at a time when Tehran is especially filled with tensions. Fueled by the weight of U.S. economic sanctions and the crush of the coronavirus pandemic, Iran has been reeling internally. Plus it is facing even more external pressures in the wake of the assassination of its leading nuclear scientist late last month

It is clear that whoever assumes the role of Iran's Supreme Leader is sole driver of the country's agenda. From diplomatic relations to military activity to a bid to fully revive its once-thriving ambitions to build a nuclear bomb, all actions could rest with someone who is not interested in the west or in the United States.

"Mojtaba Khamenei is very close with hardliners in Iran," Pourmohsen added. "I think he will not have good relations with the U.S; I guess he is harder than his father."