RIYADH, Saudi Arabia — A short midlevel cleric, with a neat white beard and a clergyman’s calm bearing, Mehdi Karroubi has watched from his home in Tehran in recent months as his aides have been arrested, his offices raided, his newspaper shut down. He himself has been threatened with arrest and, indirectly, the death penalty.
His response: bring it on.
Once a second-tier opposition figure operating in the shadow of Mir Hussein Moussavi, his fellow challenger in Iran’s discredited presidential election in June, Mr. Karroubi has emerged in recent months as the last and most defiant opponent of the country’s leadership.
The authorities have dismissed as fabrications his accusations of official corruption, voting fraud and the torture and rape of detained protesters. A former confidant of Ayatollah Ruhollah Khomeini and a longtime conservative politician, he has lately been accused by the government of fomenting unrest and aiding Iran’s foreign enemies.
Four months after mass protests erupted in response to the dubious victory claims of President Mahmoud Ahmadinejad, the opposition’s efforts have largely stalled in the face of unrelenting government pressure, arrests, long detentions, harsh sentences, censorship and a strategic refusal to compromise.
But for all its success at preserving authority, the government has been unable to silence or intimidate Mr. Karroubi, its most tenacious and, in many ways, most problematic critic. While other opposition figures, including Mr. Moussavi and two former presidents, Mohammad Khatami and Ali Akbar Hashemi Rafsanjani, are seldom heard now, Mr. Karroubi has been unsparing and highly vocal in his criticism of the government, which he feels has lost all legitimacy.
Last week, a special court for the clergy began to consider whether Mr. Karroubi, 72, should face charges. His response, in a speech to a student group that was reported on a reformist Web site, was withering.
“I am not only unworried about this court,” he wrote. “I wholeheartedly welcome it since I will use it to express my concerns regarding the national and religious beliefs of the Iranian people and the ideas of Imam Khomeini, and clearly reveal those who are opposed to these concerns.”
Despite such provocations, Iran’s conservative leadership has so far not arrested him, apparently fearful of making a powerful symbol of a man so closely associated with the founding of the Islamic republic.
“His potential arrest is an acid test of the internal meltdown of the upper echelon of the regime and the final breakdown in its legitimacy facade,” said Hamid Dabashi, a professor of Iranian studies at Columbia University. “We had heard that revolutions eat their own children, but his seems to be a case of revolutionary parricide.”
Mr. Karroubi works from a villa on a quiet street in Tehran that ends at a rundown palace once occupied by Shah Mohammed Reza Pahlavi. It is one of the many symbols of his standing among the revolutionary elite. He was jailed nine times by the shah and spent years in prison, where he grew close to inmates of widely different political persuasions: nationalist, socialist, Islamist, said Rasool Nafisi, an Iran expert based in Virginia.
“These forced companionships, Karroubi wrote in his autobiography, made him aware of the pain of the others, and relieved him from sectarian behavior,” Mr. Nafisi said.
After the overthrow of the shah, Ayatollah Khomeini put Mr. Karroubi in charge of the Imam Khomeini Relief Committee and the Martyrs Foundation, two of the nation’s most important and wealthiest institutions. He also served twice as speaker of Parliament, where he earned a reputation as a conciliator; served on the powerful Expediency Council; and was appointed adviser to the subsequent supreme leader, Ayatollah Ali Khamenei.
So it was hard for the leadership to brand him an enemy of the state when he posted on his Web site last month an impassioned, unyielding and damning letter to the nation, written in response to the judicial finding that his allegations of the rape of imprisoned protesters were unfounded.
“The ugliness has reached the point that instead of the perpetrators and propagators and people behind this oppression, it is Mehdi Karroubi whom they want to put on trial,” he wrote. “I take refuge with you, oh God, from these catastrophes which some are causing and are not only a disgrace to the Islamic republic, but a disgrace to Iran.”
Mr. Karroubi’s disenchantment with the revolution he helped create began not with the elections in June, but with the balloting that brought Mr. Ahmadinejad to office four years ago. Mr. Karroubi was a candidate then, too, and late into the night after the polls closed, he was running second, behind Mr. Rafsanjani.
A few days later, he talked about election night during an interview in his villa, still angry and surprised at what had happened. He said he had gone to sleep and when he woke, he was in third place, behind Mr. Ahmadinejad and out of the race.
Mr. Ahmadinejad won a runoff, and Mr. Karroubi wrote an open letter of protest to the supreme leader charging vote fraud. There was no investigation, however, and Ayatollah Khamenei chastised Mr. Karroubi. He dropped his protest, but quit the Expediency Council and started his own political organization, the National Trust Party.
Of course, much the same thing happened again in June, when Mr. Ahmadinejad supposedly won with 63 percent of the votes cast — including 71 percent of the votes cast in Mr. Karroubi’s home province, Lorestan.
If Mr. Karroubi had restricted his complaints to the vote tally, he might have been ignored. But he has gone far beyond that with his accusations that state security officers raped, sodomized and tortured men and women who were arrested for taking part in the protests. The allegations have unnerved the leadership, threatening its legitimacy and religious standing far more than images of the police beating protesters in the streets.
After the government dismissed those allegations last month, Mr. Karroubi was summoned to appear before a three-judge panel investigating his actions. He welcomed the invitation. “It will be a good opportunity for me to talk again about crimes that would make the shah look good,” he said, according to the Green Freedom Wave Web site.
As calls for his arrest grow louder, he remains defiant.
“If only I were not alive and had not seen the day that in the Islamic republic, a citizen would come to me and complain that every variety of appalling and unnatural act would be done in unknown buildings and by less-known people: stripping people and making them face each other and subjecting them to vile insults and urinating in their faces,” he wrote in his letter to the nation. “I said to myself, ‘Where indeed have we arrived 30 years after the revolution?’ ”