Wheeler spent a stint at the EPA in the early 90s, across the George H.W. Bush and Clinton administrations, receiving agency awards for his work in 1993 and 1994. Wheeler then shifted to the Senate, serving as a staffer for Republican Jim Inhofe of Oklahoma for 15 years. Inhofe says climate change is a hoax and that the EPA is an activist organization that burdens businesses.

Wheeler’s grandfather was a coal miner, and Wheeler’s interest since leaving his Senate staff position have been firmly in favor of the coal industry and coal country. His most notable stint was for Murray Energy Company, one of the nation’s largest coal-mining companies, according to The Washington Post. Murray Energy proposed to Vice President Mike Pence in March 2017 a number of environment reversals, including exiting the Paris climate change agreement, which Trump has initiated, and killing off the Obama-era Clean Power Plan, which the EPA under Wheeler said it would weaken.

Since taking charge of the agency on an interim basis, Wheeler has pursued a lower key and less confrontational style than Pruitt, and has postponed some of the changes introduced that environmentalists and many states have objected to most strongly. This includes reversing Pruitt’s action on his final day in office, which would have allowed the continued unlimited sale of “glider kits,” or trucks retrofitted with outdated engines that can produce 20 to 55 times as much air pollution as engine emissions required under current regulations.

Wheeler required Senate confirmation for his role as deputy EPA administrator, which he received in a 53 to 45 vote in April 2018 that included three Democratic senators’ ayes. He requires another Senate confirmation to assume the role on a permanent basis.

Before joining the EPA in April, Wheeler acted as a consulting principal at international law firm Faegre Baker Daniels, and he has lobbied for Whirlpool, Sargento, and a number of other chemical and big oil interests, according to records compiled by ProPublica. The non-profit news organization notes that during his tenure on the Senate Committee on Environment and Public Works, “[Wheeler] worked on every major piece of environmental and energy-related legislation before Congress for over a decade.”

Wheeler said he would recuse himself from decisions that involved companies he once represented, and told the New York Times in August that he hadn’t asked for or received any ethical waivers that would allow him to avoid recusal.

While a lobbyist, Wheeler worked, along with Interior Secretary Ryan Zinke, to open part of Utah’s Bears Ears National Monument for uranium mining.

The potential permanent EPA administrator’s previous affiliations also include serving as the vice president of the Washington Coal Club, an organization made up of 300 coal producers, lawmakers, and energy industry executives, according to environmental policy non-profit the National Resources Defense Council.

Before starting his EPA rule earlier this year, Wheeler was active on Twitter. He almost entirely ceased posting new messages, but occasionally retweets a Republican or non-partisan source, including actress Ruth Buzzi twice. His most recent original message simply notes “RIP #johnmccain RIP” on the date of that senator’s death.