When a young and radical Shiite cleric discussed plans here last week to set up his own government of Iraq, he challenged more than the American-led occupation.
The cleric, Moktada al-Sadr, threatened the authority of the four grand Shiite ayatollahs who hold sway in this holy city and who until now have counseled the 15 million Iraqi Shiites to remain patient with foreign troops.
Many Shiites say Mr. Sadr overreached in his proclamation and defiance of the occupation. But he has highlighted the enormous authority that the ayatollahs have over the Shiites. Whether the clerics' patience holds may be the most important variable that determines whether the United States succeeds in Iraq.
"The Shia Islamist clerics are going to have a lot to say, and probably are ultimately going to dominate Iraq," said Kenneth Katzman, senior Iraq analyst for the Congressional Research Service. A broad call by the ayatollahs for a Shia, or Shiite, uprising would be "a worst-case scenario for the occupation that would create major, major problems for the United States," Mr. Katzman said by telephone from Washington.
The Shiite Muslim community stretches 400 miles south from Sadr City, a vast slum on the northern edge of Baghdad. Najaf, about 100 miles south of the capital, is its spiritual and theological center, home to the shrine of Imam Ali, whose assassination led to the founding of Shiism.
The Shiites make up about 60 percent of all Iraqis, and since Saddam Hussein's government fell in April, Mr. Sadr has tried to tap this silent majority to lead opposition to the occupation.
At first glance, he might seem a natural choice. While only 30, he has substantial support among the Shiites, mainly because his father, Muhammad Sadiq al-Sadr, was a widely revered ayatollah who was killed by Mr. Hussein's men in 1999.
Followers of Mr. Sadr and another radical cleric have killed five American soldiers in the last two weeks, a stark reminder of the danger that a broad Shiite revolt would present to the occupation. But Mr. Sadr appears to have overestimated his appeal — and underestimated the loyalty that ordinary Shiites feel to the grand ayatollahs of Najaf, especially Ayatollah Ali Sistani.
"We look to Sistani like a father," said Ahmed Mehdi Mohssen, who owns a small fruit stand in Najaf. "Whatever he will say, we will do."
All across southern Iraq, Shiites echo Mr. Mohssen's words. "Sistani represents Islam," said Saad Abdul Zahra, a businessman in Basra, Iraq's main southern city. "I will follow his call."
The reach of the ayatollahs extends beyond managing mosques and holding prayer services. They hand out welfare payments, hold courts that can judge both religious and civil offenses, mediate disputes between tribes, and rule on basic aspects of daily life.
In a nation with few heroes, the faces of clerics stare out from posters taped to rear windows of cars on the highways from Baghdad to Basra. The ayatollahs are not quite a shadow government, but they are much more than just religious icons.
They generally occupy modest houses protected by polite, if well-armed, guards, and rarely speak in public, both to maintain mystique and safety. But two of the four grand ayatollahs made their sons available for interviews last week, and a third, Ayatollah Sistani, answered several written questions.
After a generation of repression under Mr. Hussein, the grand ayatollahs are not ready to call for an uprising against the occupation, especially since the Shiites have now regained religious freedom, including the all-important right to make pilgrimages to Najaf, they said.
"The Iraqi people are so deprived, and they've been suffering for a long, long time," said Sheik Ali al-Najafi, the son of Grand Ayatollah Bashir al-Najafi. "We want to spare them another war," he added, implying that loyalists of Mr. Hussein's Baath Party were trying to foment trouble.
The Baathists "will disguise themselves in all different titles and all different ways," he said. "They even created their own movements, and they made those movements look like they've been fighting the Baathists, so when the Baathists go, those movements will have credibility."
Alaa al-Hakim, the son of Grand Ayatollah Muhammad Saed al-Hakim, said the Shiites should remain patient. "According to our traditions, patience is one of the most important foundations of our faith," he said. "This patience is not a feeling of defeat. It's a sign of courage."
In his statement, Ayatollah Sistani also implicitly criticized Mr. Sadr's call to form a government, saying that only a democratically elected government could rightly rule Iraq and that clerics should not have final authority over the government.
Mr. Sadr has not been helped by his style. He travels with numerous bodyguards, who have a habit of pushing bystanders around. His greatest political asset is probably the respect Shiites hold for his father, but he is neither particularly charismatic nor old enough to claim encyclopedic knowledge of the Koran. A botched effort by his supporters last week to seize two mosques in Karbala, about 50 miles south of Baghdad, appears to have further drained his support.
Last Thursday, a sunset protest march in Najaf by supporters of Mr. Sadr drew only about 500 demonstrators. As they walked toward the golden-domed mosque that holds the tomb of Imam Ali, whose death in 661 A.D. opened the split between Shiite and Sunni Muslims, they drew hard stares from many shoppers.
Mr. Sadr "should not have formed the new government yet," said Madih Adel, who repairs watches in the central square. "He doesn't have many supporters in Najaf."
Mr. Sadr's strongest support is in Sadr City, home to two million Shiites. "I will follow Moktada," said Hussein Muhsen, a carpenter, as he smoked a cigarette in a Sadr City tea shop on Sunday. But even there Mr. Sadr's support is far from universal. A majority of Muslims, said Aiyad Musa, a barber, "are just looking at Sistani, waiting for one word to follow."
The main noon prayer service in Sadr City last Friday, the first weekly service since Mr. Sadr proclaimed his new government, illustrated both the strengths and the limits of his support. At least 10,000 people attended. Under a hot sun, Abdul Hadi Darraji, a cleric in Mr. Sadr's organization, exhorted the crowd to support the young cleric. "Yes, yes, Moktada," they shouted. Mr. Darraji stirred them further, saying that enemies of Islam had used the Sept. 11 attacks to control Iraq. Again the chants boomed. "No, no, America!" "No, no, occupiers!"
But the crowd was actually smaller than it had been a week earlier, before Mr. Sadr proclaimed his government. At the end of the service, Mr. Sadr's supporters changed the direction they marched to avoid American tanks guarding a government building.
For now, Mr. Sadr's challenge has pushed the grand ayatollahs into an uneasy allegiance with the occupying forces. The clerics interviewed refused to set a deadline for the forces to leave, or outline what could turn them openly against the Americans, but in general they sounded far from friendly to the United States.
"We refuse their presence as we refuse the presence of Saddam Hussein," Mr. Najafi said. Mr. Hakim said the United States should "speed up the ending of the occupation, and make the right conditions for the Iraqis to be able to govern themselves."
All Grand Ayatollah Sistani would reply was, "Each incident will bring its response."