Washington ? America’s viceroy in Baghdad, retired Army Lt. Gen. Jay M. Garner, told my Washington Post colleagues Peter Slevin and Monte Reel last week that he does not anticipate great difficulty in managing Iraq’s transition to democratic self-government.

“To get them comfortable with self-government I don’t think will take long,” Garner said. “Once they’re comfortable with it and they realize where they are and what they have, I think they’ll take off. I have high hopes for this.”

Optimism is an admirable trait, but if you want a more sober assessment of what lies ahead in liberated Iraq, listen to Senate Foreign Relations Committee Chairman Dick Lugar. The Indiana Republican told NBC’s “Meet the Press” that U.S. taxpayers should be thinking about a five-year effort, at least, to put Iraq back on its feet. And if you really want to grasp the challenge facing the American occupation force, turn to a newly published report from the Carnegie Endowment for International Peace titled “Political Reconstruction in Iraq: A Reality Check.”

The authors, Marina Ottaway of Carnegie and Johns Hopkins University and Judith Yaphe of the National Defense University, point out that “Iraq is not a political blank slate, to be transformed at American will into a democratic, secular, pluralist and federal state.”

“Instead,” they say, “it is a difficult country with multiple social groups and power centers with conflicting agendas … adding to the problems of reconciling rival ethnic and religious factions as well as internally and externally based opposition elements.”

Lugar’s concern, first voiced well before the start of hostilities, is that the Bush administration gave far less thought to preparing for postwar Iraq than it did to fashioning a successful battle plan. Unfortunately, events in the early going already have proved him right.

Iraqis, along with scholars around the world, are blaming the U.S. military for failing to safeguard the national treasures in Baghdad’s main museum and library or to halt the looting once it began. Americans are also being faulted for delays in restoring electricity, water and other services. Already, Sunni Muslims, who enjoyed a preferred position under Saddam Hussein, have mounted a mass march demanding the departure of U.S. troops, while clerics of the rival and more numerous Shiite Muslim faith, backed by armed bands, have taken de facto control of local governments in parts of the country not being run by the Kurds, who must also somehow be integrated into a new Iraqi nation.

As Ottaway and Yaphe write, “U.S. military and civil administrators initially will have inordinate power in deciding how to deal with Iraq’s disparate social and political groups.” But in the absence of any single leader who commands respect from all those groups, the U.S. inevitably is trying to establish a broad-based interim governing council.

“But coalitions have been inherently unstable and short-lived in Iraq,” they write. “A period of martial law — hopefully short — will probably be necessary. … Martial law, however, cannot foster longer-term political, economic or social reconstruction.”

The main challenge, they say, will be to develop “a common Iraqi national identity” powerful enough to counteract the many tribal, religious and ethnic rivalries in the country. The risk is that this identity will be forged around a common antagonism to the United States and its occupation forces.

The lack of advance planning, which Lugar decried, shows in the officially denied reports that the Pentagon plans to keep permanent military bases at four sites in Iraq, in order to enhance its strategic position in the Middle East, while others in the administration want to see troops withdrawn within months.

The Carnegie authors suggest that the U.S. not rush the process of creating a new government or scheduling elections and that the political reconstruction of Iraq, and especially the management of its rich oil resources, be made an international responsibility — something that would require General Garner and the Pentagon to share power.

Optimism may soon be another shortage in Iraq.

Correction: The singing judge never sang. Contrary to the news clippings I found in his file at the Senate Judiciary Committee, Judge Edward Prado of San Antonio, whose elevation to the 5th Circuit Court of Appeals I commended in a column last week, did not entertain lawyers and spectators by singing a version of a Turtles song in breaks of a murder trial. Instead, he played a parody of the Turtles song “Happy Together,” a recording performed by the Bar and Grill Singers of Austin, satirizing the conceit of a judge who says, “Imagine me as God. I do.”

I received e-mails on the subject from several lawyers who had heard the recording and I confirmed this with Judge Prado, who — though no vocalist — will bring great distinction to the bench.