"The split is very old and it has caused a lot of tragedy," said Abd-Kareem al-Mahamedawy, one of Amara's most prominent political leaders and a moderate Shiite.

But many moderate Shiites have called for Mr. Sadr and his militia to leave Najaf, and there were no signs of wider unrest on Friday.

Shiites, who compose about 60 percent of Iraq's 25 million people, stand to gain most from any future democratic government here, and Mr. Sadr represents a divisive danger to that goal for many moderate Shiites.

Some moderate Shiites are already accusing Mr. Allawi, a secular Shiite, of being too close to certain groups.

And that has led to a struggle in many cities between religious conservatives and moderate Shiites who advocate a more pluralistic, secular approach.

"We need the moderate Shiites to take charge of the streets and their own future," a U.S. commander in Iraq told me.

If resistance is expressed for the sake of a just Islamic state, both moderate Shiites and Sunni Muslims will reject the call as religious radicalism.

Some moderate Shiites have tentatively endorsed the changes in the name of stability and reconciliation.

"There's no democracy in Iraq," Mr. Yasseen said, expressing the deep suspicions of moderate and secular Shiites.

The Iraqi National Congress, a group of opposition leaders that includes moderate Shiite as well as Kurdish leaders, has stressed its support for the territorial integrity of Iraq and for democratic principles.