When Biden leaves the race, Sen. Bernie Sanders, I-Vt., will claim the mantle of front-runner, Lewandowski predicted Wednesday on "The Todd Starnes Show."
"I am fully convinced Joe Biden is not going to be the Democratic nominee," he said.
"Is he really the Hillary Clinton of the 2020 race? The answer is yes. He's running a campaign telling everyone that he's the only one who can beat Donald Trump and the truth is he can't win a primary.
"Joe Biden is going to lose that nomination. I believe he'll be out of the race by South Carolina."
Following up, host Todd Starnes asked the political operative if he believed someone more liberal will win the nomination instead.
Lewandowski agreed, naming Sanders and labeling him, "truly a socialist."
"I still think it's going to be Bernie Sanders," he said, adding anyone claiming the label of "socialist" will lead to President Trump, "winning in a landslide."
Earlier this week, Biden released a financial disclosure form along with three years of tax returns.
The documents showed Biden raked in millions since leaving office.
He and his wife, Jill, made more than $11 million in 2017 before taxes and made more than $4.5 million in 2018 before taxes. Biden's campaign said that the vast majority of that income ($10,048,739 in 2017 and $3,236,764 in 2018) derived from payments to the couple for the writing of two books: Joe's “Promise Me, Dad” and Jill's “Where the Light Enters,” as well as paid speaking engagements.
Biden’s first book, an account of his son Beau’s death from cancer, topped bestseller lists in 2017.
The former senator, who was never one of the wealthier members of Congress during his decades on Capitol Hill, has seen his fortunes turn considerably since the end of Obama administration.
Fox News' Frank Miles contributed to this report.