The Gallup poll released Wednesday said that independents are especially likely to have changed their minds in the wake of the advances made by the Islamic State of Iraq and Syria. Their approval of President Obama's action has dropped by 18 percentage points since 2011, while among Democrats and Republicans approval went down by 9 and 10 points.
ISIS' seizure of major cities has not, however, changed attitudes towards the 2003 invasion under President George W. Bush. The new poll found 57 percent believe sending troops to the country in 2003 was a mistake with no significant change since a February survey.
Gallup found that 61 percent still support the 2011 withdrawal, down from 75 percent at the time. Among Democrats, 87 percent back the president, as do 59 percent of independents and only one-third of Republicans.
The poll was conducted on June 20 and June 21. The president announced he was sending 300 military advisers to Iraq while the poll was underway.
Gallup interviewed 1,012 adults by telephone. The margin of error is 4 points.