Harris aides on Wednesday evening had told CNBC on condition of anonymity that they had "reason to believe that a conversation happened and are continuing to pursue it."

Harris, D-Calif., had grilled Kavanaugh on Wednesday about whether he had any contact with members of Kasowitz's firm regarding Mueller's special counsel investigation into whether the Trump campaign colluded with Russian operatives during the 2016 presidential election. Kavanaugh appeared confused during the late-night questioning.

"There have been no discussions regarding Robert Mueller's investigation between Judge Kavanaugh and anyone at our firm," a spokesman for Kasowitz said in a statement first provided to CNBC on Thursday.

Marc Kasowitz, a personal attorney for President Donald Trump , threw cold water on Sen. Kamala Harris' questioning of Brett Kavanaugh, denying he had any contact with his firm, Kasowitz Benson Torres.

Kavanaugh himself addressed the issue again Thursday morning. "I don't recall any conversations of that kind with anyone at that law firm," he said during his hearing.

The Kasowitz denial came as Sen. Cory Booker's own attempt at making waves in the Kavanaugh hearing appeared to have fallen flat. Harris and Booker, D-N.J., are both considered possible contenders for the Democratic presidential nomination in 2020.

Harris' office did not return requests for comment on Kasowitz's statement. On Thursday, she told a CNN reporter that Kasowitz's denial wasn't "under oath." She did not elaborate, according to the reporter.

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Throughout Thursday, several Kasowitz associates told CNBC that they had never witnessed Kavanaugh having any interaction with attorneys at the firm.

Mark Corallo, a former spokesman for Kasowitz, said that while he worked with Kasowitz through July 2017, he had never seen Kavanaugh mix with his team.

"Never in my three months had anyone mentioned Brett Kavanaugh's name and not since, either," Corallo said.

A friend of Kasowitz who spoke on condition of anonymity, said that Kasowitz and Kavanaugh come from two different types of legal cloth, making any chance of a conversation between the two very minimal.

"Kasowitz is an aggressive attorney who at times worked for a guy like Trump," this person said. "Kasowitz is a totally different venue compared with Kavanaugh."