Sam Clovis this week withdrew his name from consideration to be the top scientist at the Department of Agriculture amid revelations about his connection to the ongoing Russia probe.

Clovis, a former conservative radio talk show host in Iowa, was nominated by President Donald Trump to be the Agriculture Department's undersecretary for research, education and economics. His Senate confirmation hearing had been tentatively scheduled for next week, but had been imperiled as questions mounted about his activities as national co-chairman of Trump's presidential campaign.

“The political climate inside Washington has made it impossible for me to receive balanced and fair consideration for this position,” Clovis wrote in a letter to Trump dated Nov. 1, according to The New York Times. “The relentless assaults on you and your team seem to be a blood sport that only increases in intensity each day.”

As recently as Tuesday, the White House had expressed no concern about Clovis' nomination.

"I'm not aware that any change would be necessary at this time," press secretary Sarah Huckabee Sanders said.

Following Clovis' withdrawal, Sanders said Thursday: "We respect Mr. Clovis's decision to withdraw his nomination."

Clovis' attorney confirmed to The Washington Post that he is the "campaign supervisor" mentioned in court documents involving George Papadopoulos, the former Trump campaign foreign policy adviser who pleaded guilty to making false statements to the FBI and is cooperating with Justice Department special counsel Robert Mueller's investigation into possible collusion between the campaign and Russia.

Court documents show Papadopoulos in 2016 attempted to arrange a meeting between the Trump campaign and Russian officials, with Clovis at one point responding to his efforts with an email stating, "Great work." Later, regarding efforts to set up an "off the record" meeting with Russian officials, Clovis wrote to Papadopoulos, "I would encourage you" to "make the trip, if it is feasible."

Clovis' attorney, Victoria Toensing, said in a statement that Clovis "always vigorously opposed any Russian trip for Donald Trump and/or the campaign," adding that his responses to Papadopoulos were merely the courtesy of "a polite gentleman from Iowa."

Clovis also came under scrutiny after the Post on Thursday published his responses to various questions from Sen. Debbie Stabenow of Michigan, the top Democrat on the Senate Agriculture, Nutrition and Forestry Committee, which is handling his nomination.

Federal law specifies that the person tapped for the undersecretary position be chosen "from among distinguished scientists with specialized training or significant experience in agricultural research, education, and economics," as the job is "responsible for the coordination of the research, education, and extension activities of the Department."

"Please list all graduate level courses you have taken in natural science," the letter states.

"None," Clovis wrote.

The next directive: "Please list all membership and leadership roles you have held within any agricultural scientific, agricultural education, or agricultural economic organizations."

"None," Clovis wrote.

And a third: "Please describe any awards, designations, or academic recognition you have received specifically related to agricultural science."

"None," Clovis said.

In response to another question – "What specialized training or significant experience, including certifications, do you have in agricultural research?" – Clovis, who has a doctorate in public administration and reportedly has taught classes on topics like business management and public policy, pointed to his experience as a college professor and running twice for office in Iowa.

"I bring 17 years of agriculture experience integrated into both undergraduate- and graduate-level courses throughout my teaching career as reflected in my curriculum vitae as well as the Committee's questionnaire," he said, adding that "one cannot be a credible candidate in [Iowa] without significant agricultural experience and knowledge."

He also said he was a contributor to "the development of the successful undergraduate agricultural program at Morningside College" in Sioux City, Iowa.

Clovis has called climate-change science "junk science" and "not proven," and has faced criticism over suggesting gay-rights protections could lead to protecting pedophilia.