More than eight in 10 people oppose the war in Afghanistan, according to a recent CNN survey.
The poll released Monday found 17 percent of people supported the war, while 82 percent opposed it.
A similar poll in 2008 found 52 percent supported the war, while 46 percent opposed it at the time.
Another 57 percent said the war is going badly, while less than one in three people said the United States is winning.
CNN polling director Keating Holland said the numbers indicate the Afghanistan war could be the most unpopular in history.
"Opposition to the Iraq war never got higher than 69 percent in CNN polling while U.S. troops were in that country, and while the Vietnam War was in progress, no more than six in 10 ever told Gallup's interviewers that war was a mistake," Holland said.
The poll conducted earlier this month follows a pattern of polling showing dwindling support for the conflict. A Washington Post-ABC poll released earlier this month found two-thirds of the public said the war had not been worth fighting — including a majority who expressed strong beliefs.
U.S. and NATO forces are set to hand off security control to Afghanistan in late 2014.
The U.S. has been trying to secure a security agreement with the country that would leave as many as 10,000 troops in the country in a training capacity after the 2014 deadline.
The CNN poll surveyed 1,035 people and has a 3 percentage point margin of error.