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Newly hired MSNBC host Symone Sanders appeared to take a swipe at a new colleague Wednesday, claiming parts of his book about President Biden's path to the White House were "not true." 

The former chief spokesperson for Vice President Kamala Harris made the claim about reporter Jonathan Allen's book "Lucky" during an appearance on "The Rachel Maddow Show" while reacting to a passage concerning Biden's campaign promise to nominate a Black woman to the Supreme Court.

Symone Sanders, Vice President Kamala Harris and DHS Secretary Alejandro Mayorkas

Vice President Kamala Harris walks with Department of Homeland Security Secretary Alejandro Mayorkas and Spokesperson Symone Sanders to board Air Force Two at El Paso International Airport in El Paso, Texas, June 25, 2021. (REUTERS/Evelyn Hockstein/File Photo)

SYMONE SANDERS, A TOP KAMALA HARRIS ADVISER, RESIGNING AMID SIGNS OF VP OFFICE DISARRAY

"Well, let me ask you if the account in that book is broadly correct. Did you and other advisers to President Biden think that that was not the right move, when he made that pledge at that debate, on that debate stage in South Carolina?" host Rachel Maddow asked, referencing Allen's passage claiming Sanders told Biden not to make the commitment during a South Carolina Democratic primary debate.

"Well, I will note a number of those things in that book are not true, but that is in fact true. There was lots of debate in the lead-up to that debate in South Carolina in February about what then-candidate Biden should do," Sanders responded. "There was never a question about if the commitment was real."

She added that the book was also true in claiming Biden's team didn't want him making such a commitment to look as if he was "pandering" to Black voters.

Sanders didn't go into detail as to what other aspects of Allen's book weren't true. 

Symone Sanders speaks onstage during Global Citizen Week: At What Cost? at The Apollo Theater on Sept. 23, 2018, in New York City.

Symone Sanders speaks onstage during Global Citizen Week: At What Cost? at The Apollo Theater on Sept. 23, 2018, in New York City.   (Getty Images)

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Biden made the commitment to nominate a Black woman for the Supreme Court while speaking during the February 2020 debate ahead of the South Carolina Democratic primary. 

Following the commitment, Biden received House Majority Whip Jim Clyburn's, D-S.C. endorsement, which helped revive his flailing campaign and ultimately helped secure a win for him in the state. Biden then stormed to a series of Super Tuesday victories and cruised to the nomination.

Biden now has to decide who he will nominate to replace retiring Supreme Court Justice Stephen Breyer, who is expected to formally announce his retirement Thursday.