NAJAF, Iraq -- On one side of the grinding political deadlock over who should lead Iraq's next government is a fiery icon of the downtrodden with an exalted family name: al-Sadr.
On the other is a wizened mullah whose al-Hakim clan founded Iraq's largest political party and whose scholarly air belies a reputation for ruthlessness.
The two men are on opposing sides of the dispute over whether Ibrahim al-Jaafari should retain his post as prime minister. The impasse, unresolved despite months of negotiation and intense US pressure, hinges not only on myriad political factors but on the two clerics' family feud.
Moqtada al-Sadr and Abdul-Aziz al-Hakim head the two leading dynasties of Iraq's Shi'ite Muslim majority, whose spiritual home is this ancient southern city. They operate the country's two largest Shi'ite militias -- the Mahdi Army and the Badr Brigade, respectively -- each with more than 10,000 men. And they are heirs to rival movements that for generations have competed, sometimes violently, for supremacy among their long-persecuted people.
''Iraqi clerical Shi'ism tends to run in families and has for a long time," said Juan Cole, a University of Michigan professor and specialist on Shi'ite Islam. ''Throughout the 20th century the Sadr and Hakim families have been maybe the most prominent examples and have vied for influence. Here they are again."
Their divergent politics mean the dispute over the prime minister's post has wide-ranging and complex implications for the future of Iraq, and for the US presence here.
The coalition of Shi'ite parties that won the most votes in Iraq's Dec. 15 elections has nearly fractured over its choice of Jaafari as nominee for prime minister. Sadr, whose political allies control about 30 seats in the new Legislature, has lined up behind Jaafari, believing him more likely to push the Americans to depart Iraq soon. Hakim's Supreme Council for the Islamic Revolution in Iraq, which also holds about 30 seats, has been working to install its own candidate, Adel Abdul Mahdi.
Despite being groomed for decades by the government of Iran, Hakim has largely embraced the United States since the 2003 invasion and has profited from it. His Supreme Council party works closely with US Ambassador Zalmay Khalilzad and controls several ministries in Iraq's lame-duck transitional government.
Sadr, meanwhile, has battled the US presence. In 2003, an Iraqi judge issued a murder warrant for Sadr in connection with the killing here of a rival cleric with ties to the United States. Two years ago, his Mahdi Army militiamen fought US forces here and in Baghdad. US diplomats and commanders say they number Sadr and his militia among the gravest threats to Iraq's security, and none has met with him directly.
''We will never negotiate under occupation," said Sayyid Riyadh Nouri, who heads Sadr's political committee and is married to the cleric's sister. ''We do not participate with people who violate our democracy."
Sadr and his followers paint the Supreme Council as a foreign movement; its founders were exiled in Iran when Saddam Hussein ruled Iraq. In an interview with a
''The difference is simple: The Hakim family decided to get out of Iraq to fight the former regime, while the Sadr family stayed inside and openly defied Saddam," said Sahib al-Amiry, head of the Sadr-run God's Martyr Foundation. He denied frequent reports that Sadr also receives substantial support from Iran. ''Our only relationship with Iran is as a neighbor," he said.
Both Sadr and Hakim owe their strength to a mix of religious legitimacy and impeccable bloodlines. Both wear the black turban that signifies their status as putative descendants of the Prophet Mohammed.
Sadr lost brothers, an uncle and his father, Grand Ayatollah Mohammed Sadiq Sadr, at the hands of Hussein's Sunni-dominated security forces. Hakim says more than 60 family members were killed in recent decades -- including his brother, former Supreme Council leader Mohammed Bakir al-Hakim, who was obliterated by a car bomb outside Najaf's Imam Ali shrine in 2003. In the past half-century, members of both families have held the revered rank of grand ayatollah, the top position in Najaf's Shi'ite religious hierarchy.