Bernie Sanders has a lot to gain in the 2020 Democratic presidential primary race if Joe Biden's poll numbers continue to slip, according to Matt Schlapp.

While African-American voters continue to support Biden at the highest level of all other candidates, the former vice president and U.S. senator from Delaware still has a lot to lose, Schlapp said Tuesday on Fox News' "The Ingraham Angle."

"In most of these polls, it shows the number two pick of Biden voters is Bernie Sanders," Schlapp, chairman of the American Conservative Union, told guest host Raymond Arroyo, referring to the U.S. senator from Vermont.

"So what you're really seeing is potentially African-American or black voters getting behind Kamala [Harris] while Bernie will benefit from some other voters if Biden continues to have shaky performances."

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Schlapp attributed Biden's slip in the polls to his debate performance last week.

In that debate, Sen. Harris, D-Calif., confronted Biden about comments he made about working with segregationist former Sens. Herman Talmadge, D-Ga., and James O. Eastland, D-Miss.

Schlapp claimed Harris's exchange appeared to double as a way for Harris to gain some ground among African-American voters.

"To me... it seemed like at some point, one of these black candidates was going to stand up and have the moral voice to try to pull these voters back," he said.

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Arroyo pointed to recent polling from Quinnipiac University, which showed Biden holding 31 percent support among African-American voters, Harris with 27 percent, Sen. Elizabeth Warren, D-Mass., with 4 percent and South Bend, Ind., Mayor Pete Buttigieg with zero.

Schlapp added he believed the nation's economic performance under President Trump will ultimately unite voters no matter their racial or ethnic background.

"The idea that you have more economic opportunities is a big deal," he said.