Lawmakers from both sides of the aisle appeared to breathe a collective sigh of relief following Scott Pruitt's resignation as administrator of the Environmental Protection Agency (EPA), but new battle lines were beginning to form around Andrew Wheeler, a former coal industry lobbyist who is taking the reins on an interim basis beginning Monday.

Pruitt resigned Thursday in the wake of numerous allegations of abuses of power. In a letter to President Trump, Pruitt wrote that he was resigning because of "unrelenting attacks on me personally..."

Wheeler was confirmed by the Senate last April as deputy EPA administrator. It was unclear if President Trump would nominate him for the top job on a permanent basis, or if Wheeler was even interested in the post.

"The president has not indicated whether Wheeler might have the job permanently, nor whether the White House might eventually seek to fill the top post with an outsider," analysts with ClearView Energy Partners LLC said in a note to clients Thursday. Under the 1998 Federal Vacancies Reform Act, Wheeler could lead the EPA on an interim basis for some time.

"With looming mid-term elections and a slim GOP Senate majority, vetting and confirming a new nominee from outside EPA could prove difficult," ClearView analysts said. "As it stands, President Trump would not need to make any decisions until the next Congress."

Wheeler previously served as chief of staff for Sen. James Inhofe (R-OK), and worked at the EPA during the George H.W. Bush and Clinton administrations. He most recently worked as a principal at FaegreBD Consulting. He also is a former lobbyist and has represented Murray Energy Corp., which has sued the EPA over proposed changes to National Ambient Air Quality Standards.

EBW Analytics CEO Andy Weissman said for environmentalists, Pruitt's resignation "could be a classic case of 'be careful what you wish,'" considering Wheeler's background in the coal industry.

"Wheeler has promised to recuse himself from EPA matters pertaining to the coal industry," Weissman said Friday. "This restriction, however, could prove to be narrow in scope, confined to matters directly pertaining to coal mines. On issues pertaining to use of coal at power plants and climate change broadly, Wheeler is likely to be just as aggressive as Pruitt, if not more so."

The oil and gas industry had a more nuanced reaction to Pruitt's departure.

"The alleged scandals had become a distraction for Administrator Pruitt," said Western Energy Alliance President Kathleen Sgamma. "We have full confidence that Andrew Wheeler will continue the positive EPA agenda of actually following the Clean Air Act, Clean Water Act and other bedrock environmental laws rather than imposing overreaching red tape not based in law."

Inhofe, Pruitt's most ardent supporter, said the former EPA head "was single minded at restoring the EPA to its proper statutory authority and ending the burdensome regulations that have stifled economic growth across the country. I was pleased to work with him on critical issues, like pulling out of the Paris cClimate agreement and prioritizing the cleanup of Superfund sites."

Inhofe added that Wheeler, who had worked for him for 14 years, "is the perfect choice" to lead the EPA. "I have no doubt and complete confidence he will continue the important deregulatory work that Scott Pruitt started while being a good steward of the environment."

RFS Concerns Remain

Some Republicans also appeared happy to see Pruitt go, especially those representing Midwestern states, where his efforts to overhaul EPA's Renewable Fuel Standard (RFS) crossed a red line.

"Administrator Pruitt's ethical scandals and his undermining of the president's commitment to biofuels and Midwest farmers were distracting from the agency's otherwise strong progress to free the nation of burdensome and harmful government regulations," said Sen. Chuck Grassley (R-IA). Rep. David Young (R-IA) added that Pruitt "hurt Iowa farmers by recklessly undercutting" the RFS.

ClearView analysts said "without Pruitt, we think the EPA could become less inclined to pursue RFS reform. We also think the agency might potentially make more sparing use of the small refiner exemptions that have been weighing on biofuels credits, particularly after the quagmire these decisions created.

Wheeler’s background began to resonate with some Democratic lawmakers shortly after Pruitt's departure.

"Elevating former coal lobbyist Andrew Wheeler to head the EPA is only trading one fossil fuel friend for another," said Sen. Edward Markey (D-MA). "We must continue to fight the fossil-fuel entrenched interests that have gripped the EPA and want to undermine the public's health and progress on climate action."

Sen. Elizabeth Warren (D-MA), in a Facebook post Friday, said Wheeler "may not have the same stink of blatant corruption as Scott Pruitt -- but he's just as dirty." In a separate post on Thursday, she quipped that Pruitt "should have resigned 28 scandals ago."

Environmental groups were already lining up against Wheeler.

"Andrew Wheeler is equally unqualified to serve as the nation's chief environmental steward," said Natural Resources Defense Council spokeswoman Ana Unruh Cohen. "Like Pruitt, this veteran coal lobbyist has shown only disdain for the EPA's vital mission to protect Americans' health and our environment."

Sierra Club Executive Director Michael Brune said "credit is due to the many Americans on both sides of the aisle" for speaking out against Pruitt, whom he called "one of the most corrupt officials in the history of our nation." But Wheeler is not the person to replace Pruitt, he said. “Senators must confirm a nominee who will hold the health and safety of American families in higher regard than the profits of big polluters."