The 87-year-old Republican has told people that he will step down at the end of the year, four years before his term is up. His seat is likely to stay in G.O.P. hands.
Andrew Wheeler, who will run the agency now that Scott Pruitt is gone, is known for opposing environmental regulations. But unlike Mr. Pruitt, he is known for staying out of the limelight.
The Senate on Thursday confirmed the Environmental Protection Agency’s second-in-command, Andrew Wheeler, a former coal lobbyist who shares the deregulatory zeal of Scott Pruitt, the agency chief.
Mr. Pruitt may be using his position as an environmental deregulation czar to position himself to run for office in Oklahoma — or perhaps the presidency.