Seventeen years into the U.S. military mission in Afghanistan, Americans remain pessimistic about U.S. efforts in the country. About half of adults (49%) say the United States has mostly failed in achieving its goals there, while about a third (35%) say it has mostly succeeded, according to a new Pew Research Center survey. Another 16% say they do not know if the U.S. has succeeded or failed.

In surveys conducted in 2014 and 2015, opinions about the mission were similarly more negative than positive. Between 2009 and 2011, when asked whether the U.S. will succeed or fail to achieve its goals, majorities said the U.S. would be successful.

Republicans are now more optimistic than Democrats that the U.S. mission in Afghanistan has succeeded in achieving its goals, according to the new survey, conducted Sept. 18-24 among 1,754 adults. About half of Republicans and Republican-leaning independents (48%) say the U.S. has succeeded, compared with about three-in-ten Democrats and Democratic leaning independents (28%).

Three years ago, during the presidency of Barack Obama, partisan opinions were nearly the reverse: 42% of Democrats said the U.S. had succeeded, compared with 29% of Republicans.

As the initial decision to use military force in Afghanistan grows more distant, public opinion has become more divided on whether it was the right decision or wrong decision. Today, 45% say the U.S. made the right decision in using military force and 39% say it was the wrong decision.

The share of Americans saying the initial decision was right has declined over time. In 2006, 69% said it was the right decision and 20% said it was the wrong decision. (On a different question asked in early 2002, a few months after the start of the war, 83% of Americans said they approved of the U.S.-led military campaign against the Taliban and Al Qaida in Afghanistan.)

Republicans have consistently expressed more support than Democrats for the decision to use force in Afghanistan (as well as in Iraq), though support has fallen in both parties over the past decade. About two-thirds of Republicans and Republican leaners (66%) now say it was the right decision to use force in Afghanistan. Only about a third of Democrats and Democratic leaners (31%) say the same. About half of Democrats (53%) say it was the wrong decision, compared with 21% of Republicans.

Note: See full topline results and methodology here (PDF).