The CNN/ORC International survey released Monday also indicates that a majority of Americans would like to see U.S. troops pull out of Afghanistan before the December 2014 deadline.
Just 17% of those questioned say they support the 12-year-long war, down from 52% in December 2008. Opposition to the conflict now stands at 82%, up from 46% five years ago.
"Those numbers show the war in Afghanistan with far less support than other conflicts," CNN Polling Director Keating Holland said. "Opposition to the Iraq war never got higher than 69% 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."
The U.S. timetable for Afghanistan calls for the removal of nearly all troops by roughly this time next year, and that can't come fast enough for the vast majority of Americans. Just over half would rather see U.S. troops withdrawn earlier than December 2014. Only a quarter say that America should still have boots on the ground in Afghanistan after that deadline.
Fifty-seven percent say the conflict is going badly for the U.S. and only a third say America is winning the war in Afghanistan.
"Independents have a much gloomier view of the war in Afghanistan than Republicans or Democrats," Holland said. "That may be because a Republican president started the war and a Democratic president has continued it, so there may be some residual support among people who identify with either party."
Some 2,300 U.S. troops have been killed in Afghanistan since the war began in the autumn of 2001. The U.S. is quickly drawing down its forces in Afghanistan. If a bilateral security agreement that would keep up to 10,000 U.S. troops in Afghanistan after the end of 2014 isn't signed in the near future, the U.S. could withdrawal all forces from Afghanistan at the end of next year.
The poll was conducted for CNN by ORC International between December 16 and 19, with 1,035 adults nationwide questioned by telephone. The survey's overall sampling error is plus or minus three percentage points.
The discontent evident in the CNN poll is also seen in two other national surveys conducted earlier this month. Two-thirds of those questioned in an ABC News/Washington Post poll said the war has not been worth fighting, and an Associated Press/GfK survey showed 57% saying the U.S. did the wrong thing in going to war in Afghanistan.
CNN Political Editor Paul Steinhauser contributed to this report.