Pollster Nancy Zdunkewicz said on Monday that voters believe President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE is weak on the issue of foreign policy, which she said could end up hurting him in 2020.

"One big weakness among Republicans and Trump voters was the large number of people saying that he was worse than expected on foreign policy issues," Zdunkewicz, managing editor at Democracy Corps, told Hill.TV's Jamal Simmons on "What America's Thinking," referring to a new Hill-HarrisX survey.

"So that will be something that will be raised a lot in a general election campaign, and where he is vulnerable in his own party and among his own voters," she continued.

The poll, which was released on Monday, found that 43 percent of voters surveyed said Trump performed "worse than expected" on foreign policy, while 21 percent said he performed "better than expected."

Twenty-seven percent of voters said the president had performed about what they had expected.

Other polls have also shown Trump lagging in foreign policy.

A new Associated Press-NORC Center for Public Affairs Research poll found that 63 percent of respondents disapprove of Trump's handling of foreign policy, while 35 percent said they approved.

Trump made headlines when he announced his decision to pull U.S. troops from Syria last year, and declared victory against Islamic State in Iraq and Syria in the war-torn country.

Democrats and various Republicans slammed the decision, saying the U.S. mission had not yet been accomplished in Syria.

— Julia Manchester