Former oil and gas lobbyist David Bernhardt was confirmed by the Senate on Thursday to lead the Interior Department, an agency that controls nearly half a billion acres of public land and the vast amount of oil and gas mineral resources resting beneath it.

The 56-to-41 vote Thursday promoted Bernhardt from Interior’s acting secretary, a job he assumed after his predecessor, Ryan Zinke, resigned amid numerous investigations into his behavior and management of the agency. Bernhardt had served as Zinke’s deputy until his departure in December.

The vote tally made Bernhardt the Interior Department’s least popular nominee for secretary in 40 years, according to the Center for American Progress, a liberal-leaning policy institute. Before Thursday, Zinke had the most votes in opposition, 31. Before President Trump’s two picks, every nominee over that time received fewer than 25 no votes, the group said.

Bernhardt’s extensive experience at Interior, where he served as solicitor during the George W. Bush administration, was cited by his supporters who said he is more than qualified to lead the agency.

But his work as a lobbyist for the oil and gas industry in the West, as well as large water utilities, led to concerns about conflicts of interest. The Interior Department oversees 700 million acres minerals and other resources underground and 1.7 billion acres offshore. The department works closely with some of Bernhardt’s former clients.

Bernhardt has so many potential conflicts of interest that he carries an index card listing companies and people he should avoid. Concerns over ethics led to a heated confrontation between a Democrat who opposed Bernhardt’s nomination and a Republican who supported it at his confirmation hearing.

Sen. Ron Wyden (D-Ore.) said Bernhardt came to his office and assured him that he would follow ethics rules. Shortly after the meeting, Wyden said, he was startled to see that Bernhardt was the subject of a newspaper article that said he intervened on behalf of the oil industry and others to stop a U.S. Fish and Wildlife Service analysis that said certain toxic pesticides used by such businesses threatened endangered animals.

“Why would you come to my office and lie?” Wyden asked. The actions “make you sound like just another corrupt official,” the lawmaker said.

Wyden’s statement was immediately countered by Bernhardt’s friend and fellow Coloradan, Sen. Cory Gardner (R), who said Democrats exhibited a double standard by supporting former interior secretary and petroleum engineer Sally Jewell but not Bernhardt.

In the end, the Energy and Natural Resources Committee approved Bernhardt’s nomination by a 14-to-6 vote. Several Democrats joined Gardner in supporting the nominee.

A woman wore a swamp creature mask during the Senate confirmation hearing for interior secretary nominee David Bernhardt on March 28. (C-SPAN)

A day before the vote by the full Senate, Sen. Martin Heinrich (D-N.M.) explained his support for Bernhardt.

“I need to be able to pick up the phone and talk to the secretary of interior on a regular, regular basis because these things have direct impacts on New Mexico,” Heinrich said Wednesday. “We didn’t win the election in 2016, so I’m not going to get my choice for secretary of interior. In the meantime, I have to be able to work with these folks.”

Heinrich expressed particular concern about potential oil and gas drilling in the Chaco Canyon area near massive stone ruins considered sacred to the descendants of the ancient Pueblo civilization.

“I’m going to put my state, and the protection of public lands in my state, ahead of the sort of political battle that happens in Washington, D.C.”

On the day of the Senate vote, Gardner again denounced Bernhardt’s opponents and said the “Washington, D.C., political smear machine has been working overtime” to bring down a good man.

Democrats and conservation groups in turn say Bernhardt has worked overtime to roll back key regulations protecting public lands and wildlife.

With Bernhardt acting as an influential deputy under Zinke, Interior held oil and gas lease sales that resulted in more than a billion dollars in revenue for the national treasury.

But the agency also weakened enforcement of the 100-year-old Migratory Bird Treaty Act, allowing individuals and companies to kill scores of protected birds so long as investigators determine it was not intentional, reversing a long-standing rule.

The pair also oversaw a rollback of National Park Service rules on federal land in Alaska that will allow hunters to kill mother bears and their cubs sleeping in dens as well as shooting animals from boats as they swim between shores.

Interior is considering an unprecedented plan to offer federal offshore leases that could lead to drilling on nearly the entire U.S. outer continental shelf, including the Arctic and Atlantic, areas where drilling has been largely forbidden.

Five companies are seeking permits from Interior that would allow them to use seismic air guns to map the Atlantic floor in search of oil and gas deposits. Last year, the National Oceanic and Atmospheric Administration granted the companies permits that allow them to unintentionally harm or even kill marine animals while conducting operations.

Conservationists and several attorneys general representing coastal Atlantic states are fighting the NOAA permits and the applications for Interior permits in court.

Sen. Amy Klobuchar (D-Minn.) said Thursday that she opposed Bernhardt’s nomination for several reasons, including his role in weakening enforcement of the law to protect birds and “stacking the deck in favor of the fossil fuel industry.”

Like other Democrats, Klobuchar decried his actions to limit opportunities for the public to comment on Interior’s policy decisions and his directive to agency employees to not factor climate and environmental effects into guidance.

Under Bernhardt, she said, Interior has not only downplayed climate science, it has engaged in decisions and rulemaking “that will accelerate its effect. The question is not is it happening … the question is what will we do about it,” she said.

National Ocean Industries Association President Randall Luthi praised Bernhardt’s confirmation. “NOIA looks forward to working with the Department of the Interior,” Luthi said, adding that the group encouraged timely decisions on important pending offshore policies, including Atlantic seismic permits, an expanded national offshore oil and gas leasing program, and a reliable and consistent schedule of future offshore wind lease sales.

But Jamie Rappaport Clark, president and chief executive of the Defenders of Wildlife, had the opposite reaction.

“We are deeply disappointed that the Senate decided to confirm the Secretary of the Interior with a record full of ethical conflicts and unwavering allegiance to the oil and gas industry,” said Rappaport. Interior “badly needs leadership that restores the public’s trust in its mission to conserve our natural resources, not more of the same failed policies and ethical challenges that have plagued the department under this administration.”

Dino Grandoni contributed to this report.