"If the United States withdrew its forces from Baghdad’s streets this fall, the murder and mayhem would increase."

According to a NYT study:

The New York Times interviewed more than 40 Iraqi politicians and citizens and consulted recent surveys of public opinion in Iraq. The views of a broad range of senior military officials, American intelligence experts, politicians and independent analysts who have recently returned from Iraq were also solicited....

Sheik Ajmi al-Mutashar, an agricultural engineer and businessman from Salahuddin Province in central Iraq and a Sunni, said he worried that an American troop pullback would lead to the collapse of the Iraqi government. “If the government falls it will be impossible to form another one,” he said. “We will have small emirates or cantons divided on sectarian and ethnic lines.”

Several Shiites also agreed that an American pullback would severely weaken the already fragile Iraqi government and lead to an upsurge of fighting among armed factions. “Without a strong and visible American presence, the government would collapse,” said Abu Fayad, an aide to a leading Shiite member of Parliament. “Of course there will be many different wars. Basra, Diwaniya, Baghdad. Everyone will try to control Iraq’s fortune. The Americans failed, but they should stay.”

Salah Sultan al-Obeidi, 39, a government employee who lives in the Shiite stronghold of Sadr City but says he holds secular views, says he worries that moderate elements of Iraqi society would be even more vulnerable if the Americans were to leave. “In Baghdad there will be fierce fighting between Sunni and Shiite extremists. Sunni terrorists will kill all the Sunnis who took part in the political process.”...

“I think the Sadr tide will rule the country,” said Muhammad Qasim Ali, a suitcase salesman in the predominantly Shiite neighborhood of Karada. “They are the majority and they have a good background, and that gives them a chance to take control. Once we take power, we will be merciful with Sunnis. Our way is to kill somebody only when we suspect he has a link to insurgents.”