Wheeler is an energy lobbyist and former Senate Environment and Public Works Committee staffer who supporters say will bring discipline, rigor and understatement to Pruitt’s much-publicized deregulatory agenda to weaken and rewrite rules to combat climate change.

“He is a really good guy, he is very soft spoken, he works not to be flamboyant, or noticed, and he wants to keep the rhetoric down as a way of being more about efficiency and getting things done,” Myron Ebell, director of the Center for Energy and Environment at the free-market Competitive Enterprise Institute, told the Washington Examiner.

Critics say Pruitt has little to show for his regulatory campaign and has failed to back his efforts with data to show why regulations he targets are unnecessary.

Liberal attorneys general have successfully sued the Trump administration for actions including eliminating a rule to limit methane emissions, missing a deadline to implement standards for controlling smog-forming pollution, and suspending a requirement that states track on-road greenhouse gas emissions.

“Wheeler is ideal to be No. 2 at EPA to manage the agency to accomplish the Trump agenda.” said Ebell, who led President Trump’s EPA transition team. “They have needed him. The reform effort will really take off with Andrew providing the expertise.”

Wheeler’s stock was helped by support from at least some moderate Democrats, who noted their comfort level interacting with him for more than a decade when he was a top staff member on the Environment and Public Works Committee, working mostly for former Chairman Jim Inhofe, R-Okla., the Senate’s most prominent denier of climate change.

Sens. Joe Manchin, D-W.Va., who represents a major coal mining state, and Heidi Heitkamp, D-N.D., who is up for re-election in a red-leaning and shale oil-producing state, voted to approve Wheeler. Sen. Joe Donnelly, D-Ind., also backed him.

The support of at least one Democrat was crucial because Republicans hold a one-seat majority in the Senate, and Sen. John McCain, R-Ariz., is on leave to receive cancer treatment. Sen. Tammy Duckworth, D-Ill., also did not vote, because she is on leave after giving birth.

Democrats also could take satisfaction that Wheeler vowed to respect the views of EPA’s career staff.

EPA employees are among “the most dedicated and hard-working employees in the federal government,” Wheeler said in his confirmation hearing. “The mission of the EPA to protect human health and the environment is critical to our country and its citizens and something that I take very seriously and I know you do, too.”

But some Democrats wanted the vote to be delayed to vet Wheeler more thoroughly, as the White House reportedly is looking for him to take over if Pruitt is fired.

“We should be having a full-blown debate, not this truncated process that’s being imposed upon us here today,” said Sen. Ed Markey, D-Mass., speaking on the Senate floor Thursday. “It’s like a shadow confirmation vote for the next administrator of the EPA.”

Sen. Tom Carper of Delaware, the top Democrat on the Environment and Public Works Committee, said it will be Wheeler’s job to “right these wrongs” that Pruitt has created amid scandals.

Democrats who oppose Wheeler note his past lobbying work for Murray Energy, the largest privately-owned coal company in the U.S.

“I’m firmly against Andrew Wheeler’s nomination,” said Sen. Kamala Harris, D-Calif. “We should not put a coal lobbyist second-in-command at the Environmental Protection Agency. That is absurd.”

Those who have worked with Wheeler say those criticisms are unfair, and note he has experience on Capitol Hill working on a bipartisan basis. Wheeler also worked from the EPA 1991 to 1995 on toxic chemical issues.

“He certainly agrees with this administration’s perspective on environment and energy issues,” said Dave Conover, vice president of public affairs at Kinder Morgan, who worked with Wheeler on the Environment and Public Works Committee. “There is not any question he shares those values, but he was able to do pretty impressive stuff on a bipartisan basis.

“If Jeb Bush was president and he nominated Andrew Wheeler, the political rhetoric against him would be a lot lower.”