This Thursday morning, President-elect Donald Trump officially named Scott Pruitt, the Oklahoma attorney general and a friend of the fossil fuel industry, to head the Environmental Protection Agency. The selection suggests a remarkable and dangerous shift in the agency's direction given Pruitt’s past collaborations with oil and gas companies and the lawsuits he has filed against major health and environmental policies in the past eight years, including lawsuits against the EPA itself. On his LinkedIn page, Pruitt describes himself as “a leading advocate against the EPA’s activist agenda.”

“Scott Pruitt running the EPA is like the fox guarding the hen house,” League of Conservation Voters’ president Gene Karpinski said in a statement. “Time and again, he has fought to pad the profits of Big Polluters at the expense of public health. He’s sued the EPA over commonsense safeguards like the Clean Water Rule and Clean Power Plan and sent letters to federal officials that were written almost entirely by the oil and gas industry. And like fellow Oklahoman senator Inhofe, Pruitt is an outright climate denier who has ignored settled science for political points.”

Pruitt began his political career as a Republican state senator in Oklahoma in 1998. In 2001, he ran and lost in a bid for a seat in the U.S. House of Representatives. He remained a state senator until 2006, when he ran and lost in a race to become lieutenant governor. He began his turn as Oklahoma attorney general in 2011. One of his first actions was a lawsuit against the Affordable Care Act. He gained notoriety among environmentalists in 2014 when an investigative report by the New York Times revealed that he had taken a three-page letter from Devon Energy—one of Oklahoma’s biggest oil and gas companies—changed a few words and passed it off as his own and then forwarded it to the EPA. The letter said that federal regulators were grossly overestimating the air pollution caused by new gas wells in Oklahoma.

In July 2015, Pruitt gained more attention when he filed a lawsuit against the EPA that was meant to stop the Clean Power Plan, a measure that would cut carbon dioxide pollution from power plants by 32 percent from 2005 levels by 2030. “The EPA does not possess the authority under the Clean Air Act to accomplish what it proposes in the unlawful Clean Power Plan,” he said in a statement. “The EPA is ignoring the authority granted by Congress to states to regulate power plant emissions at their source. The Clean Power Plan is an unlawful attempt to expand federal bureaucrats’ authority over states’ energy economies in order to shutter coal-fired power plants and eventually other sources of fossil-fuel generated electricity.”

Pruitt eventually joined another lawsuit against the Clean Power Plan with 27 other states. That lawsuit may well make it to the Supreme Court. Pruitt remarked earlier this year on the importance of Trump’s victory to the lawsuit’s possible success. “This election in November is consequential for many reasons, but the most consequential reason, from my estimation, is the control of the U.S. Supreme Court going forward," Pruitt said at the Conservative Political Action Conference last March. "We must have another Justice Scalia on the Supreme Court.”

Pruitt has also been a key opponent of the EPA’s Clean Water Rule, which increases the number of streams and wetlands protected under the Clean Water Act. Traditionally, under the Clean Water Act the federal government regulated the nation’s navigable waters and seas. In June 2015, the EPA issued the Clean Water Rule, which added the regulation of streams, ditches, ponds, creeks, wetlands, and high water marks related to those bodies of water. In July 2015, Pruitt filed a lawsuit against the EPA with the goal of having the rule declared unconstitutional.

While many environmental groups raised alarms about the nomination, conservative think tanks like the Heartland Institute cheered the pick. “Pruitt has sued the Environmental Protection Agency over its Mercury and Air Toxics Standards Rule, its Waters of the United States Rule, and the Clean Power Plan,” the organization said in a statement. “So it seems there is hope the next administration will finally rein in the runaway EPA—by withdrawing or rewriting those and other rules in a way that respects freedom and economic progress, or by deciding not to defend the rules in court. One small appointment for Trump, one giant leap for environmental sanity.”

Pruitt has received more than $340,000 from energy and natural resources companies since he first ran for office. Despite the fact that 97 percent of scientists agree about human-made climate change, Pruitt speaks about the reality as something that is still being debated. “Healthy debate is the lifeblood of American democracy, and global warming has inspired one of the major policy debates of our time,” he wrote in the National Review with Alabama attorney general Luther Strange. “That debate is far from settled. Scientists continue to disagree about the degree and extent of global warming and its connection to the actions of mankind. That debate should be encouraged—in classrooms, public forums, and the halls of Congress.”

That denial of climate change, his record as an ally of fossil fuel companies, and his lawsuits against the EPA made many Democratic politicians speak out against Pruitt’s nomination. “The EPA has the enormous responsibility of protecting our environment and keeping Americans safe and healthy,” said Hawaii senator Brian Schatz in a statement. “Its administrator should share those goals, but Scott Pruitt’s record has shown us that he does not. While the EPA is tasked with protecting our people and our environment from the impacts of climate change, he denies the science behind it. And while the agency has worked to keep our air and water clean and safe, Scott Pruitt has worked to undermine the very rules that protect those resources.”

Pruitt has repeatedly pushed back against federal environmental regulations and spoken up for the rights of states to regulate industry. If he makes it through the confirmation process, many of the federal environmental gains made during the past eight years could be lost or weakened. For example, Trump can’t eliminate the new rules created during the Obama administration aimed at reducing greenhouse gas emissions from power plants, but the EPA chief could weaken, delay, or take them apart. “During the campaign, Mr. Trump regularly threatened to dismantle the EPA and roll back many of the gains made to reduce Americans’ exposures to industrial pollution, and with Pruitt, the president-elect would make good on those threats,” said Ken Cook, the head of the Environmental Working Group, in a statement.