No one in Najaf wore a bigger smile to the polls Saturday than Falah Hassan Sarraf.

The electrical engineer and his wife were so keen to vote in Iraq's constitutional referendum that they hardly slept the night before, he said. And they brought along their three young daughters to share in the moment.

But when asked what they liked so much about the document, which even the Shiite Muslim politicians who dominated its drafting have acknowledged is far from perfect, Sarraf gave what turned out to be a common response in this Shiite spiritual center.

"We are with the marjiya," he said, referring to the members of the highly influential Shiite religious council that asked followers to support the referendum. "If they say 'Vote yes,' we vote yes."

Millions of Iraqis voted similarly Saturday on a referendum issue that appears to have passed despite intense opposition from Sunni Muslims, although final results have not been released. Even as the former dictatorship moved to the brink of formalizing its rebirth as a nation of laws, voters across southern Iraq, home to some of the world's most sacred Shiite cities and shrines, left little doubt that their loyalties lay with the country's clerics and not its politicians. On polling day in Najaf, where local officials say more than 80 percent of voters backed the constitution, a majority of those interviewed said they had never read a word of it or knew little or nothing about its contents.

"There are two types of authority: political and religious. And of the two, religious is higher," said Mohammad Khuzai, a representative of Bashir Najafi, one of Iraq's four top Shiite clerics, whose rulings on religious, cultural and occasionally political matters can carry more force than law.

But turnout in Najaf and across Shiite-majority southern Iraq was far lower than expected Saturday. An estimated 50 percent of the roughly 450,000 eligible voters in Najaf province went to the polls, compared with more than 80 percent in January's landmark legislative elections. That raised the prospect that the dictates of Shiite clerics had lost some weight since January, when they declared voting an Islamic duty and endorsed Shiite religious parties such as Dawa and the Supreme Council for the Islamic Revolution in Iraq.

Those parties earned overwhelming support from voters, but the government they formed in late April has disappointed many Iraqis by failing to improve the country's infrastructure and security in nearly six months in office.

"The marjiya tell us, 'Say yes,' but I don't see any purpose," said Abbas Father, an unemployed resident of Karbala, a city west of Najaf that is home to the shrine of Imam Hussein, whose death in battle there in the 7th century was a pivotal event in the history of Shiite Islam.

"They told us last time to support the alliance and I did," Father added, referring to the clerics' tacit endorsement of the Shiite coalition that won a majority in parliament. "What did we get?"

Under Saddam Hussein, Shiites were relegated to second-class status. Their clerics largely eschewed politics -- partly in keeping with the dominant "quietist" strain of Shiite thought and partly to survive.

They emerged into public life after the U.S.-led invasion with new freedoms and an undiminished following. To the surprise of U.S. officials here, Grand Ayatollah Ali Sistani, the marjiya's most influential member, soon called for democratic elections.

Across southern Iraq today, the clerics' faces adorn T-shirts, posters and signs along highways and main streets. Ubiquitous graffiti declare "Yes, yes Sistani." By comparison, the visibility of Shiite political leaders, such as Prime Minister Ibrahim Jafari of the Dawa party, is virtually nonexistent.

But the clerics -- and particularly the marjiya, who constitutional negotiators say were deeply involved behind the scenes in the drafting process this summer -- have recently curtailed public involvement in politics, observers say. Before Saturday's vote, Sistani "urged" Shiites to support the constitution, using language that fell short of the order he issued in January.

"It was a suggestion, not a must," said Bushra Zamili, who oversaw all the referendum polling centers in Najaf province. "We were hoping for a stronger statement encouraging people to vote, but it did not come."

Muhammed Hamuzi, secretary of the Najaf branch of Iraq's Communist Party, one of the country's oldest political institutions, said he believed the marjiya were withdrawing from politics because they feared their reputation had suffered from involvement in the last election.

"The government that came out of it has failed. I am not saying that people do not still follow the marjiya, because they do, but clearly in this referendum many people did not follow their instructions, even Sistani's," Hamuzi said. "People are following political leaders more than before, rather than religious ones."

Observers here say that some of the top clerics' status has been usurped by Moqtada Sadr, an outspoken and influential younger cleric with a fervent following among poor Shiites in slums across the country. A militia loyal to Sadr, whose slain father was a member of the marjiya, fought U.S. troops in Najaf and Karbala last year, and he has repeatedly called for the withdrawal of American forces from Iraq. Because Sadr, who is believed to be in his early thirties, has not attained a lofty religious rank, his adherents also follow other clerics. But many pledge their highest loyalty to him.

"I follow Sayyid Moqtada because he is wise in religion and wise in politics and he stands up to the occupier," said Hassan Abdul Salaan, 20, a laborer. He attended one of the nightly feasts to break the Ramadan fast that Sadr, who did not take a public stance on the constitution, sponsored at a Najaf mosque in the week leading up to the referendum.

Some Shiite political leaders in Najaf say that the public follows leaders, religious or political, for what they say, not who they are.

"These days I think it depends on their opinions. If the marjiya's opinions are better, people will follow them. If the politicians' are better, they will follow them," said Sadr Aldeen Qubunchi, the top official in Najaf for the Supreme Council.

But as Ali Merza, the Dawa party representative in Najaf and a Koranic scholar, points out, there is often little difference between the two camps. Qubunchi, for example, is also the imam of Friday prayers at Najaf's most prominent mosque.

"The political leaders are religious leaders, and the religious leaders are also political leaders," Merza said.

That notion concerns some U.S. and Iraqi officials. Some Shiite leaders have proposed forming a state from among the Shiite-populated provinces across southern and central Iraq, a possibility enabled by the constitution's endorsement of federalism. Jafari and other Shiite leaders have criticized the plan, as have Sunni Arabs who fear it could lead to the dissolution of Iraq. Clerics here could have significant control over what form such a state takes, a possibility that has led to speculation they might push for a Shiite theocracy.

"In southern and central Iraq, the important people in the parties don't have enough authority to control the people," said Nawzad Hadi, governor of Irbil in the Kurdish-controlled north, which already enjoys significant autonomy. "The religious people are ruling from the mosques. It may be difficult."

Correspondent Jackie Spinner in Irbil and special correspondent Saad Sarhan in Najaf contributed to this report.

After voting Saturday, Shiites in Baghdad displayed ink-marked fingers in front of poster of Grand Ayatollah Ali Sistani.