A controversial former campaign adviser to President Donald Trump has withdrawn his name from consideration for a top post in the U.S. Department of Agriculture in the wake of reports that connected him to an investigation into Russian meddling in the 2016 presidential election.

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In a letter dated Wednesday and obtained by Politico, Sam Clovis said that he was "eternally grateful and humbled" by the president's nomination. However, he said he felt it best to withdraw his name from consideration for the USDA chief scientist post to keep from becoming a "distraction or negative influence" on the Trump administration.

"The political climate inside Washington has made it impossible for me to receive balanced and fair consideration for this position," Clovis wrote. "The relentless assaults on you and your team seem to be a blood sport that only increases in intensity each day."

White House spokeswoman Sarah Huckabee Sanders told the Des Moines Register that officials respect his decision to withdraw.

Trump nominated Clovis in September to serve as undersecretary of agriculture for research, education and economics for the USDA. He has since come under criticism for his lack of science credentials.

Clovis currently serves as the USDA’s senior White House adviser.

The undersecretary position has historically been filled by people with advanced degrees in science or medicine, The Washington Post reported. Clovis, a former Iowa talk radio host and political science professor, has a bachelor's degree in political science, a master's degree in business administration and a doctorate in public administration, according to the Post.

In a letter obtained by the Post and published Thursday, Clovis confirmed that he did not have any academic credentials in science.

Clovis has faced greater scrutiny in recent days, after federal authorities revealed that former Trump president campaign foreign policy adviser George Papadopoulos pleaded guilty earlier this month to lying to officials investigating Russian meddling in last year’s election and its possible ties to the Trump campaign.

Papadopoulos told investigators that he understood that one of the Trump campaign's main foreign policy goals was to improve relations between Washington and Moscow. To that end, he tried several times to set up meetings between Trump campaign and Russian government officials.

He failed to disclose his attempts to authorities, despite inquiries from the FBI. He pleaded guilty to lying to authorities on Oct. 5 and has since been cooperating with investigators, according to officials.

Court documents showed an unnamed "campaign supervisor" was in communication with Papadopoulos about his attempts to arrange a meeting between campaign and Russian officials. Clovis's lawyer confirmed to Bloomberg News that an unnamed "campaign supervisor" mentioned in the documents, who was in communication with Papadopoulos about his attempts to arrange a meeting between campaign officials and Russian representatives, is Clovis.

In a statement released earlier this week, Clovis said Papadopoulos "was acting on his own and that the campaign had a strict rule against traveling abroad and claiming to speak on behalf of the campaign," Bloomberg News reported.

White House press secretary Sarah Huckabee Sanders said Monday that Papadopoulos was a volunteer who had little connection to Trump. In March 2016, Trump called Papadopoulos an "excellent guy" during an interview with The Washington Post's editorial board.

"He was going through the list of names ... (and being) complimentary to the people who were volunteering on behalf of the campaign," Huckabee Sanders said.

Senate Agricultural Chairman Pat Roberts, R-Kansas, told Politico that Clovis has been "a fully cooperative witness" in the Senate Intelligence Committee's investigation into Russian meddling.

An unidentified source told NBC News that Clovis was questioned last week by investigators connected to the FBI probe.