But his support for troop withdrawal cuts both ways, reflecting a deep internal quandary in Iraq: for many middle-class Iraqis, affection for Mr. Obama is tempered by worry that his proposal could lead to chaos in a nation already devastated by war. Many Iraqis also acknowledge that security gains in recent months were achieved partly by the buildup of American troops, which Mr. Obama opposed and his presumptive Republican opponent, Senator John McCain, supported.

“In no way do I favor the occupation of my country,” said Abu Ibrahim, a Western-educated businessman in Baghdad, “but there is a moral obligation on the Americans at this point.”