Senate Intelligence Committee Vice Chair Mark Warner said Thursday on "Your World" that with President Trump's appointment of former Iowa federal prosecutor Matthew Whitaker as acting attorney general, the probability of the Mueller probe being tampered with will increase.

Whitaker, who served as departed Attorney General Jeff Sessions' chief of staff, took over control of the Mueller probe from Deputy Attorney General Rod Rosenstein.

"It's unfortunate that we all knew the president was going to try to get rid of Jeff Sessions," Warner, a Virginia Democrat, said.

Warner criticized Trump for not appointing a bureaucrat who previously got senatorial confirmation -- naming Rosenstein and Solicitor General Noel Francisco.

He said he knows little about Whitaker, other than his portrayal as a staunch "Trump loyalist."

Warner said it would be a "bright" red line crossed if Whitaker fires or hampers Special Counsel Robert Mueller.

He said that other former Trump associates Paul Manafort, Michael Cohen and Trump Organization CFO Allen Weisselberg are all cooperating with the government, and that the "public needs to see the results" of the probe.

Neil Cavuto countered that none of the three men are implicated in anything linking Trump and Russia, as Mueller's original mandate appeared to intend.

Warner said there are others in Trump's orbit like Roger Stone -- a former Nixon confidante and political consultant -- who have a "swirl" around them.

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"The chances of Mueller being interfered with goes up dramatically" with Whitaker's appointment, he said.

Cavuto said that Trump can fire or solicit resignations from anyone as chief executive.

Warner said he agreed, adding that as a former governor of Virginia, he did the same thing. But, he countered that executive terminations are open to Senate oversight.

He said that in the Old Dominion, Democrats and some Republicans agreed that Trump appears "untethered" -- appearing to allude to why Sen. Timothy Kaine (D-Va.) bested his Trump-endorsed Republican challenger, Prince William County Chairman Corey Stewart (R-Manassas).

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