The power struggle among Shiite groups in Iraq -- which has periodically erupted in bloody conflict over the past few years -- is marred by varying degrees of Iranian influence, acceptance of the elected government and cooperation with U.S. forces.

Discord between two of the main Shiite power-brokers in Iraq, the nationalist Muqtada al-Sadr and the Iranian-backed Supreme Islamic Iraqi Council, has led to skirmishes in Diwaynia, Karbala and Najaf. The Fadila Party and Prime Minister Nouri al-Maliki's Dawa Party are also components of the Shiite political calculus.

In August, al-Sadr condemned the killings of two Supreme Council provincial governors in Muthanna and Qadisiya. While he denied that his Mahdi militia was responsible, the deaths were depicted as a consequence of the rivalry among Shiites.

Juan Cole, a professor of modern Middle Eastern and South Asian history at the University of Michigan who specializes in Shiite politics, said divisions existed among Shiites while Saddam Hussein was in power, and U.S. policy-makers should not have been surprised at the intra-sectarian conflict that erupted after the U.S.-led invasion that ousted him. Literature coming out of the groups in the late-1990s described assassination plots on rival groups while they were still in Iran.

"That they would come into Iraq and not fight each other would be surprising," Cole said.

A major point of contention among Shiite powers is the degree of support for the U.S. presence in Iraq. Al-Sadr has built a populist movement out of his anti-U.S. rhetoric, while Dawa and Supreme Council leaders maintain working relationships with the United States.

Al-Sadr has been able to capitalize on widespread public discontent that troops are still in Iraq. The U.S. military surge that began earlier this year may have even helped al-Sadr purge his Mahdi militia of rogue members who would not stand down and abide by his commands, said Stephen Biddle, a senior fellow in defense policy at the Council on Foreign Relations.

"Opposition to the Americans is a tactical position he takes to further his position in Iraq," Biddle said.

A major source of division in the late Saddam era was that while the Supreme Council -- founded by Ayatollah Baqr al-Hakim and his younger brother, Abd al-Aziz -- sought refuge in Iran, the Sadrists -- led by al-Sadr's late father, Muhammad Sadeq al-Sadr, remained in Iraq and suffered. This history of Shiite oppression has become a talking point for al-Sadr and a source of empathy for his constituents.

If provincial elections were to bring a shift in power from the Supreme Council to the Sadrists, some foreign policy analysts say it would weaken Iran. While al-Sadr has cooperated with Iran periodically, his ties are no where near as close to Iran as those of the Supreme Council, whose followers have received training and support from their wealthy neighbor.

"The Supreme Council has pulled off the tightrope of being U.S.'s best ally in Iraq and Iran's best ally in Iraq. Both allies would suffer from the installment of a nationalist movement," Cole said.

Recently, the Supreme Council tried to distance itself from Iran -- the group changed its named from the Supreme Council for Islamic Revolution in Iraq to the Supreme Iraqi Islamic Council. In response to shrinking popularity in Sadrist strongholds, the Supreme Council has tried to identify more with Ayatollah Ali al-Sistani and less with Iran. Support for the Supreme Council is still strong in Najaf and Karbala, but if conditions stay the same, al-Sadr could sweep the majority of provincial elections within the next two years.

The southern city of Basra has been host to fighting between the Supreme Council's Badr Brigades and Fadila supporters. After Fadila pulled out of the United Iraqi Alliance -- a Shiite political coalition -- the provincial council passed a vote of no-confidence against Basra's governor, a member of Fadila. Al-Maliki declined to reverse the decision and Basra was left with essentially no government.

Some foreign policy and military analysts have speculated that the al-Maliki government itself is at its breaking point. A bloc of Sunni leaders walked out on the government in early August, a few months after the April departure of six cabinet ministers loyal to al-Sadr. If the al-Maliki government were to collapse, it would create a power vacuum that al-Sadr could exploit, but it is less clear whether Sadrists would retain the current government structure.

"I don't think Muqtada and his lieutenants are philosophically committed to parliamentary governance. They've decided they'll participate in it, but I think it's a pragmatic decision and not philosophical one," Cole said.

The prevailing cynicism over the Maliki government's ability the provide services for the Iraqi people has also presented an opportunity for al-Sadr to distance himself from the establishment. Electric services continue to fail, leaving millions of Iraqis without a regular source of power for the fifth summer in a row. Sadrists have avoided involvement, but if they were to assume real power in Iraq, they may not fare any better against a political structure that Biddle described as "fragmented and fear-ridden."

"I don't think there's any prospect of anybody in Iraq being able to effectively administer services," Biddle said.

For his part, al-Sadr said in an interview with the Independent that al-Maliki is "a tool for the Americans, and people see that clearly." He also said that fighting among Shiite groups -- namely in Basra -- will subside once foreign troops leave.

The concerns surrounding the Sunnis may calm eruptions among Shiites, Biddle said. But at the same time, the British troop withdrawal from Basra, which was expected to be completed by the end of August, or an even more widespread U.S. troop withdrawal throughout Iraq, would remove the main force limiting militia activities.

"The different Shiite groups in the south have tried to develop rules of the road with each other that try to minimize bloodshed, but it's hard to know how that would hold up," Biddle said.

-- By Annie Shuppy, Online NewsHour