Half a year after Iran’s disputed presidential election, the Islamic regime is suffering from partial paralysis. Despite thousands of arrests, scores of killings, widely publicized show trials, and the closure of independent-minded newspapers, the regime is seemingly reluctant to launch the kind of full-scale purge that could remove its opponents, who demand a new election and an investigation into the deaths and torture of detainees. The hesitancy of Ayatollah Ali Khamenei, Iran’s “Supreme Leader,” and his ally, President Mahmoud Ahmadinejad, is understandable. While a purge to uproot supporters of Mir Hussein Moussavi, Ahmadinejad’s main challenger in the June 12 election, could restore a semblance of stability, it might also damage the regime’s viability. For as much as they portray Moussavi as a sore loser and a saboteur trying to destabilize the Iranian state, he is a regime insider, with supporters throughout the religious and educational establishments and within Iran’s most dangerous programs.

Moussavi’s background is at odds with his new reformist stance. He pretends to have been out of politics for 20 years, returning now as an Iranian Cincinnatus to save the country from the “irrational and superstitious” Ahmadinejad. This is an affectation. Moussavi has retained his regime credentials and connections while carefully avoiding the entanglements of daily politics. For the last 20 years, he has been a member of the powerful Expediency Council, an unelected body designed to prevent the Iranian parliament from exercising any real power, though he has chosen not to attend its meetings. Like Hashemi Rafsanjani, the hardy perennial of Iranian politics, Moussavi represents the “deep state,” a network of personal, family, and professional relationships that cuts across Iran’s institutions. Unlike Rafsanjani, Moussavi has avoided conspicuous corruption.

During the election campaign, Moussavi ran on his record as a competent economic manager during the Iran-Iraq war. This dull technocratic persona masked a prime ministership from 1981 to 1989 characterized by repression. The human-rights abuses of the Moussavi era relegate Ahmadinejad’s to historical footnotes. Religious and ethnic minorities suffered particularly harsh treatment; for example, more than 200 Baha’is were executed, all Baha’i organizations were declared to be criminal in August 1983, three-quarters of Iran’s remaining Jews fled the country, and thousands were killed in a “counterinsurgency” campaign in Iran’s Kurdish regions. The cultural scene was devastated by a “cultural revolution” in which the regime violently seized control of universities, “Islamized” courses, informally barred all Baha’is from universities, threw academics out of their jobs, banned books, and rejoiced in the flight of dissident intellectuals. Indeed, Moussavi still sits on the Supreme Council for the Cultural Revolution, another membership he retains but doesn’t use. His record worries dissidents and democrats. Yet it’s precisely that bleak past that makes Moussavi a greater challenge to the state than former president Mohammad Khatami, who had once been the national librarian.

While the Islamic Republic has eliminated its enemies by the tens of thousands, internal regime purges have been limited. In 1987, the regime executed Mehdi Hashemi, a leading Islamic Revolutionary Guard Corps (IRGC) commander, after he opposed the Iran-Contra dealings with the U.S. Similarly, in June 1999, the regime disposed of Saeed Emami, an intelligence official involved in murdering dissident intellectuals. (Emami supposedly committed suicide in prison by swallowing hair-removal cream—the world’s first recorded bikini-wax suicide. After his death, Keyhan, the Pravda of Iran, implied that Emami had links to “the CIA, MI6 or Mossad.”)

A broad internal purge would be unprecedented, however, and the political cost might be too high. Already, the regime’s post–June 12 violence has exacted a political price. While worldwide public outrage greeted the killing of innocent people such as Neda Agha Soltan, the regime’s real problem is that some of its other victims were well connected. The one who counted the most was one Mohsen Ruholamini, a 25-year-old student arrested on July 9. His family was informed of his death on July 21. Officially, Ruholamini died of meningitis; actually, the police guards at the Kahrizak detention center beat him to death. Of course, not a year passes without Iranian guards killing prisoners, but Mohsen’s father is Abdol-Hossein Ruholamini, who in his youth helped seize the U.S. embassy and took American diplomats hostage on November 4, 1979. Abdol-Hossein Ruholamini has since become a leading scientist and advisor to Mohsen Rezaie, a former IRGC commander and defeated presidential candidate. Ayatollah Khamenei was forced to promise the elder Ruholamini justice for his son’s killing. Three of the guards at Kahrizak were arrested in August. The doctor on duty at Kahrizak, Ramin Pourandarjani, then died on November 10. The initial explanation, that he died of a heart attack, has been replaced with the claim that a drug overdose mixed into a salad killed him. In Iran, healthy eating has a price.

The regime would have the same difficulty dealing with Moussavi’s top advisors, one of whom is Ali Reza Beheshti. Unlike friends of Khatami who have been tortured and have spent weeks in solitary confinement, Beheshti has been arrested once and spent just five days in detention since June 12. That’s because his father was Ayatollah Seyyed Mohammad Beheshti, one of the early leaders of the Islamic revolution. Beheshti has been a revered martyr in Iran since the Mojahedin-e Khalq (an Islamo-Marxist terrorist group) assassinated him in 1981. The National University of Iran was renamed Shahid Beheshti University in his honor, and a widely circulated story claims that Ayatollah Ruhollah Khomenei—the famously callous founder of the Islamic Republic who sent thousands to die without the slightest emotion—was visibly upset by his murder.

Moussavi’s acolytes go beyond the sons of Islamic revolutionaries. He was prime minister when Iran created Hezbollah in Lebanon and then traded Western hostages for arms in the Iran-Contra affair, and his connections reach into those parts of the Iranian state that are most lethal to the U.S. and its allies. Much is made of the Iran-Iraq war veterans and IRGC officers who have prospered under Ahmadinejad. Just as important is that many of those now in the regime’s higher echelons got their start under Moussavi. Plucking his friends and associates out of the works could cripple key parts of the state, especially at the level of those managing and implementing complex projects on the nuclear and missile front.

The signs of leadership vacillation are public. With great fanfare, the regime has launched five show trials of hundreds of people, sentenced five men to die, and given others jail terms. The regime is considering legal action against Mehdi Karrubi, a twice-defeated presidential candidate, for revealing the rape of prisoners after June 12. Many of the show-trial defendants are well-known writers, academics, and former officials with reformist ideas and are associated with the ineffectual Khatami. These intellectuals have not been involved in organizing protests, nor do they have the foreign connections described in paranoid detail by the prosecution. In their coerced statements, they have fingered Moussavi, Khatami, Karrubi, and others as the culprits behind the post–June 12 unrest. Yet instead of heralding a grand show trial for Moussavi, Khamenei has backed away. In a remarkable intervention on August 27, he said, “I do not accuse the leaders of the recent incidents to be subordinate to the foreigners, like the United States and Britain, since this issue has not been proven for me.”

So the regime is slowly feeling its way forward, using standard repressive techniques that contain the conflagration without quite dousing the flames. Some of the best-known prisoners, such as former vice president Mohammad Ali Abtahi, have been convicted of the serious crime of seeking to overthrow the state—and then released on bail. The challenge facing Khamenei is both simple and intractable: with no purge, instability will continue, but with a purge, the regime can undermine itself in a way that no real or imagined CIA plot ever could.