There are few anecdotes about him, and pictures, at least ones that have appeared in public, are scarce. But Mojtaba Khamenei, the son of Iran's supreme leader, wields considerable power and is a key figure in orchestrating the crackdown against anti-government protesters, analysts say.
The younger Khamenei operates tucked behind an elaborate security structure, an overlapping world that stretches from Iran's Revolutionary Guard corps to the motorcycle-riding Basiji militiamen.
Analysts and former dissidents describe him as the gatekeeper for his father, Ayatollah Ali Khamenei, a reclusive son whose political instincts were sharpened in a post-revolutionary Iran where affiliations with security and intelligence services were just as important as Islamic ideology.
The anxiety in the streets of Tehran today goes deeper than the outrage over the June 12 election that authorities say was won by President Mahmoud Ahmadinejad -- it is the newest round in a struggle between hard-liners and reformists that began more than 20 years ago over the legacy of the 1979 Islamic Revolution.
And at the center, or at least very close to it, is Mojtaba Khamenei. Analysts say the ultraconservative cleric is being positioned to succeed his father but would face tough opposition.
Revered figures of the Islamic Revolution such as Ali Akbar Hashemi Rafsanjani and Hossein Ali Montazeri years ago deemed the senior Khamenei's religious and political resumes insufficient for him to succeed Ayatollah Ruhollah Khomeini when he died 20 years ago. However, they found themselves outflanked.
Ali Khamenei gradually has created a bureaucracy to consolidate his power over Iran's military, intelligence and foreign policy. The younger Khamenei, who is believed to be in his 40s or early 50s, working deep inside a political system that is difficult for outsiders to crack, has emerged as a force in that bureaucracy.
Mojtaba Khamenei's influence became evident when he gave key support to Ahmadinejad in the 2005 presidential election. Ahmadinejad, who analysts say shares the messianic rhetoric and Islamic fervor of the younger Khamenei, unexpectedly defeated two leading conservative candidates as well as Rafsanjani. The Khameneis are now backing Ahmadinejad against Mir-Hossein Mousavi, the opposition leader who says the June 12 election was fraudulent and should be annulled.
The Guardian Council, which oversees the electoral process, has said the outcome will stand but also announced that it will continue to investigate the disputed vote count through Monday. The street protests and violence that erupted over the last week -- state news media have reported that 10 to 19 people have died -- were in part the result of a crackdown by forces close to Mojtaba Khamanei.
"This coup taking place is a political liquidation against the old guard by reckless people like Mojtaba and Ahmadinejad," said Mehdi Khalaji, an expert on Iran with the Washington Institute for Near East Policy. "But I don't think they will win. Power that relies only on the military and doesn't care about social or religious institutions cannot last long."
Mojtaba Khamenei is a secretive man who doesn't want to "be on people's tongues," said Mohsen Sazegara, an Iranian journalist and former government official whose reformist views led to his brief imprisonment in 2003. "Nobody knows much about him."
The younger Khamenei is the "most influential person in his father's court," said Ali Afshari, a dissident and reformist who spent three years in jail for running pro-democracy programs. "The question is, what happens when his father is gone? Mojtaba needs to hold on to the security apparatus."
Khalaji, who studied in Iran's holy city of Qom, said Mojtaba Khamenei "was raised in a house surrounded by intelligence services. He doesn't have [prominent] clerical credentials, despite the fact that he wears robes and a clerical uniform."
He added that the son's background is much different from his father's. The supreme leader, in his younger years, immersed himself in literature, novels and music, was friends with intellectuals and spent time in jail with Marxists. The younger Khamenei, said Khalaji, "grew up in a very different atmosphere, a post-revolutionary generation."
Much of that generation is not grounded in the personalities and passions that underpinned the 1979 revolt.
Analysts say Mojtaba Khamenei lacks the religious and political stature to overcome the opposition he would face in the Assembly of Experts, the body charged with selecting the supreme leader. His 69-year-old father is believed to have influence over about half of the assembly's 86 seats, but the board is headed by Rafsanjani and includes other reformists who probably would block a bid by the younger Khamenei to succeed his father.
The power struggle that spilled out into the streets after the election may affect how important clerics view the younger Khamenei, and his chances of succeeding his father.
So far, the ayatollahs in Qom have been relatively quiet over the contested election and the demonstrations. But that could change if Ahmadinejad and the supreme leader press on with harsh police tactics.
"Neither Ayatollah Ali Khamenei nor Ahmadinejad are popular in Qom," Ali Ansari, the head of Iranian studies at St. Andrews University in Scotland, wrote in the newspaper the Observer. He added that Ahmadinejad is "regarded with contempt by most senior clerics, while Khamenei has never been accepted as a scholar of note. The clerics may bide their time, but their intervention, which may come sooner rather than later, especially if violence spreads, could be decisive."
Such a scenario would reduce Mojtaba Khamenei's prospects of rising to supreme leader.
"Mojtaba's hands are well into the [Revolutionary Guard] hierarchy," said Said Idriss, an Iranian expert with Cairo's Al Ahram Center for Political and Strategic Studies. "Like all conservatives, he is keen not to let any reformers reach power because then many questions will be raised regarding the financial management of the country and the billions of dollars conservatives use to support their regional political agenda.
"But I don't agree that [the younger Khamenei] is the figure behind his father's strong support for Ahmadinejad because even if Ahmadinejad is restored, it will not be easy for Khamenei to one day unveil his son as the new supreme leader."
Mojtaba Khamenei is not the only son of a supreme leader to have had political ambitions.
Ahmad Khomeini, Khomeini's son and chief of staff in the 1980s, was often regarded as a favored choice to become president. But after Khomeini's death in 1989, his son lost a power struggle with Rafsanjani, then speaker of parliament. Rafsanjani was elected president, and Ahmad Khomeini was named to the Supreme National Security Council and became caretaker of his father's mausoleum.
The younger Khomeini died of a heart attack in 1995.