John Podesta, the chair of Hillary Clinton’s 2016 presidential campaign, served as counselor to President Barack Obama and chief of staff to President Bill Clinton.

The Trump administration is among the most chaotic in U.S. history, but it is also among the most unethical, at least since that of President Warren G. Harding. The latest example came on Dec. 15 with Interior Secretary Ryan Zinke’s resignation amid a cloud of scandal as more than a dozen investigations closed in on him.

Zinke’s mismanagement of America’s public lands, natural resources and relationships with tribal nations lasted just 21 months — the shortest tenure of any president’s first interior secretary in decades (shorter, even, than James G. Watt’s in the 1980s) — but the damage will linger long after he leaves at year’s end.

Like former Environmental Protection Agency administrator Scott Pruitt, who resigned in July under similarly ignoble circumstances, Zinke is exiting to cheers of good riddance. But his leaving is not by itself a cure-all for the agency’s problems. Zinke is leaving behind a toxic culture of cronyism in the highest ranks of its political appointees. Nothing less than a full housecleaning is needed to restore public trust in the Interior Department’s leadership.

To start, there’s the oil and mining lobbyist David Bernhardt, who is now Zinke’s deputy secretary and potential successor. As Zinke jetted around the country to news conferences, photo ops and political fundraisers, Bernhardt has turned the Interior Department into a walk-in favor factory for the clients and industries for whom he used to lobby.

It is Bernhardt who is speeding past environmental reviews to lock in oil drilling in the Arctic National Wildlife Refuge, one of the world’s last truly wild places. It is Bernhardt who is dismantling Western states’ plans, designed in conjunction with a bipartisan group of governors, to conserve habitat for the greater sage grouse and other wildlife, so that the oil industry can drill wherever it wants. And it is Bernhardt who told a Post reporter that his department has little legal obligation to address climate change: “The last time I checked there was a law that said I must provide a guy to help the Department of Energy to write a report.”

Just as former coal lobbyist Andrew Wheeler, who had been serving as deputy EPA administrator, slid into the top job after Pruitt’s fall, Bernhardt reportedly has been readying himself to replace Zinke as his troubles mounted. But with a hefty list of former industry clients, Bernhardt is too conflicted to serve even one day as interior secretary.

Behind Bernhardt there is an extended cohort of political appointees who have allowed special interests to capture the Interior Department’s agenda. The head of the agency devoted to policing offshore energy development is known to give out his personal cellphone number to oil industry executives. A former adviser to industrialist Charles Koch was Zinke’s top lawyer and has issued legal opinions letting extractive businesses off the hook for damage they cause. And as The Post reported in April, someone who fought the Endangered Species Act at the behest of oil and gas companies is the top policy officer in charge of implementing this bedrock conservation law.

Zinke’s departure may briefly salve the anger and frustration of tribal nations, Western communities, sportsmen and everyone else hurt by the policies and special-interest favoritism of Trump’s Interior Department.

But the work of cleaning up and fixing the department is only beginning. To get to the bottom of the problems that Zinke is leaving behind, the Justice Department, the inspector general and the new leadership of the House committees and subcommittees with Interior oversight should work aggressively to determine how deep the corruption goes.

It is also vital for the president to immediately nominate a new secretary — one committed to the public interest and beholden to no special interests. She or he should bring in an entirely new leadership team that will rededicate the Interior Department to honoring America’s promise to tribal nations, respecting science and protecting the country’s lands and waters.

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