"Within the Agency Scott has done an outstanding job, and I will always be thankful to him for this", Trump wrote.
Sen. Tom Udall of New Mexico, one of the most relentless and vocal of Pruitt's Democratic critics in Congress, said he expects more of the same with Wheeler as chief.
"I made those comments during my time working on the Rubio presidential campaign", Wheeler said in a statement to The Hill.
The prospect of more EPA rollbacks even after Pruitt is gone is "really, really worrisome to me", he said.
Pallone last month accused Pruitt's EPA of "betraying the bipartisan effort" that led to passage led to a law updating federal chemical regulations and was named for the late U.S. Sen. Coming into office as a critic of EPA and a climate skeptic, Pruitt moved aggressively to scale back Obama-era moves on climate change, automobile pollution standards and other industrial pollutants.
Sen. Jim Inhofe (R-Okla.) was Pruitt's mentor and staunch supporter until he could no longer face the endless ethical transgressions of his former protege.
As recently as June 8, Trump praised Pruitt, telling reporters on the South Lawn of the White House that the EPA administrator was "doing a great job within the walls of the EPA", and that "we're setting records".
Pruitt has been buffeted by numerous revelations about extravagant spending, including $1,560 for a dozen fountain pens, $3,000 on "tactical pants" and "tactical polos", $43,000 on a soundproof phone booth for his office and $120,000 on a trip to Italy.
Widespread disgust for Pruitt "should serve as a blaring red siren for the Trump administration", Udall said.
"Scott Pruitt was the worst EPA administrator in the history of the agency".
Wheeler "has the potential to be just as destructive", said Michael Mikulka, president of the American Federation of Government Employees Local 704. He had also enlisted his staff to contact conservative groups and companies to find a lucrative job for his unemployed wife, including emails seeking a Chick-fil-A franchise from a senior executive at the fast-food chain. His firm was paid $300,000 past year.
Pruitt faced several federal investigations, including those for misusing taxpayer funds and for renting a room from the wife of a lobbyist with business before the EPA, as he carried out Trump's agenda of rolling back environmental regulations.
"We're proud of him for that", Pollard said.
People in Pruitt's home state differed on whether the ethics scandals in Washington left him with any prospects of a political second life in Oklahoma.