Fifty-nine percent of those queried say an end to the U.S. combat role is unlikely to occur by the announced date, a Rasmussen Reports national telephone survey found.
Rasmussen Reports says those findings include 10 percent who said it is "very unlikely" the combat mission in Iraq will end by Aug. 31 and 20 percent who answered it is "not likely at all."
Voters are closely divided over whether the war in Iraq will be regarded as a success or a failure, the polling found.
Thirty-three percent of those surveyed said America's mission will be judged a success while 36 percent said it would be viewed as a failure.
The remaining 31 percent said they were unsure.
The survey of 1,000 likely voters was conducted July 5. It carries a margin of error of plus or minus 3 percentage points.