GOP pollster says Trump must make 2020 challenger appear more unfavorable

President TrumpDonald John TrumpTrump: 'I will not let Iran have nuclear weapons' Rocket attack hits Baghdad's Green Zone amid escalating tensions: reports Buttigieg on Trump tweets: 'I don't care' MORE must make his 2020 opponent appear more unfavorable than he is if he wants to win reelection, Republican pollster Ed Goeas said Tuesday.

Goeas, who is head of the Tarrance Group, told Hill.TV's Jamal Simmons on "What America's Thinking" that 2016 Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonDe Blasio pitches himself as tough New Yorker who can take on 'Don the con' From dive bars to steakhouses: How Iowa caucus staffers blow off steam Warren policy ideas show signs of paying off MORE "had over a 50 percent unfavorable on Election Day."

"It is the first time in the history of modern-day politics that we've been able to tell that either of the nominees had over a 50 percent unfavorable rating, and both did," Goeas said. "The one given we know is Trump's going to have over a 50 percent unfavorable rating. And for him to have an opportunity to win, it's not who he's running against, it's who he's able to make more unfavorable."

Trump had an unfavorable rating of 61 percent heading into the 2016 presidential election, while Clinton was at 52 percent, according to Gallup

The Real Clear Politics average for Trump's disapproval rating put the president at 53 percent on Tuesday.

The field of candidates seeking the Democratic nomination is becoming increasingly crowded, with more contenders expected to announce their candidacies in the coming weeks and months.

—Julia Manchester