Viewers of Tuesday's fourth Democratic primary debate were unimpressed with former Vice President Joe Biden's answers on controversial allegations against his son Hunter Biden, pollster Lee Carter said Wednesday.

Appearing on "Fox & Friends" with hosts Steve Doocy, Ainsley Earhardt, and Brian Kilmeade, Carter said Biden failed to properly address the charges against his son at a moment when he needed to reassure voters.

"Biden really needed to address this last night. He needed to hit this out of the park, and he did not," said Carter, the president of Maslansky & Partners.

Carter broadcast her "voter dials," which assess the real-time reactions to the debate from voters across the political spectrum, rating statements from A to F.

WATCH: JOE BIDEN STUMBLES OVER WORDS DURING DEBATE

"Democrats just gave this a C -- not very good for them -- Independents a D, Republicans a D as well...Just not a lot of movement," she explained.

On Tuesday, Hunter Biden broke his silence in his first televised interview since his overseas business dealings came under scrutiny, maintaining he did nothing improper while he served on the board of a Ukrainian gas company.

The younger Biden said he did not discuss the Burisma Holdings board seat with his father, except for one "brief exchange" that was previously reported.

A photo obtained by Fox News last month showed Joe Biden and Hunter golfing in the Hamptons with Devon Archer, who served on the board with Hunter. Joe Biden had told Fox News that he never discussed his son’s foreign business dealings with him.

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"Biden had to stand apart last night. He really had to make a difference. He had to address this allegation," Carter told the "Friends" hosts.

"What we heard from voters last night is, 'This seems inconsistent with what his son himself said.' And, I'm not so sure that he made any kind of an impact, and I think we're going to see him continue to peter in the polls," she said.

Carter predicted that current frontrunner Elizabeth Warren, D-Mass., will continue to soar in the polls and others will plateau.

Fox News' David Montanaro and Gregg Re contributed to this report.