Sen. Chris Van Hollen Christopher (Chris) Van HollenCongress must finish work on popular conservation bill before time runs out Democrats fear Russia interference could spoil bid to retake Senate Mid-Atlantic states sue EPA over Chesapeake Bay pollution MORE (D-Md.) on Sunday urged the White House to let special counsel Robert Mueller complete his federal probe into Russia's election meddling, saying Republicans are making a "concerted effort" to undermine its credibility.

"The question is what are they afraid of? What is the White House afraid of? Let's let [investigators] finish the job and get the facts," Van Hollen said on ABC News's "This Week."

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"I think Republicans should end their concerted effort to undermine the credibility of the Mueller investigation. You've got somebody who, by all accounts, who is an independent person, somebody who's got lots of integrity and you see a concerted effort out of the White House to undermine the investigation," he continued.

"I really hope our Republican colleagues will not join in subverting that process and trying to end this investigation," he said.

Van Hollen's comments come as Republicans have pounced on the investigation after a series of text messages showing an anti-Trump bias from two FBI officials previously serving on Mueller's team surfaced from the 2016 presidential campaign.

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