Interior Secretary Ryan Zinke's departure means a change at the top, but not necessarily a change in the department's direction or the investigations involving the Montanan.
Zinke's second-in-command, David Bernhardt, is a department veteran who crafted the Trump administration's plans for Interior during the 2016 transition. Since his confirmation as deputy secretary in the summer of 2017, Bernhardt has played a key role in consequential decisions.
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Next steps for Zinke and the department
The weekend announcement by President Donald Trump -- that Zinke would leave the administration "at the end of the year" -- left many details unclear.
The natural successor on a temporary basis is Bernhardt. Trump said in his weekend post that he "will be announcing the new Secretary of the Interior next week."
Zinke -- a former Navy SEAL commander and lawmaker -- has not publicly said what he will do next.
While still on the Interior job, he professed no plans to run for governor of Montana in 2020. He has not spoken publicly since the announcement, but a source familiar with the situation said they believe he is not interested.
His spokesman did not respond to a request for comment on his plans or on his tenure as secretary.
The investigations will continue
The Interior Department Inspector General's Office will continue its investigations into Zinke, according to a spokeswoman.
The inspector general is probing whether Zinke improperly allowed political influence to block an American Indian tribe from opening a casino in Connecticut, a move that requires his department's approval.
Investigators are also reviewing conversations between Zinke and Halliburton Chairman David Lesar about a land development project in Zinke's hometown of Whitefish, Montana.
Issues raised during the Whitefish probe were referred to the Justice Department, which considers whether to file and prosecute a criminal case, CNN reported in October.
The acting secretary
Bernhardt would come to the acting secretary position with years of experience in the upper echelon of the Interior Department, and an entire career spent in natural resources law.
He held a variety of positions -- including counselor to the secretary, deputy chief of staff and solicitor, the department's top attorney -- over eight years in the George W. Bush administration's Interior Department.
After that, he represented water and energy clients for a DC law and lobbying firm -- work that left him with a long list of companies and individuals with whom he is barred from meeting or dealing, such as energy giant Halliburton Energy Services and his former law firm. The Washington Post reported last month that Bernhardt carries a credit-card-sized version of the list around as a reminder of the pitfalls.
He returned to Interior to lead the Trump administration's transition team, a role that involves selecting political appointees and identifying policy priorities.
Since his confirmation as deputy secretary, Bernhardt has led the work on a number of those policy areas.
Among them: opening federal opportunities for oil and gas drilling, revamping the application of the Endangered Species Act and re-examining water rights in the Western US.
While Bernhardt has operated without some of Zinke's flash -- such as Zinke's questionable use of government travel resources -- an Interior Department under his leadership may not differ substantially on policy lines.
Another potential candidate
Sen. Dean Heller, a Nevada Republican who lost his bid for re-election, is also said to be under consideration for the post.
Heller has cast federal land management as a top issue while in office, and he advocates for more comprehensive use of the country's energy resources.
Documents filed in a lawsuit against Zinke and the department say Heller was involved in a department decision that remains under inspector general investigation.
Heller and a Nevada congressman urged Zinke to reject the proposed casino in Connecticut, according to the court filing. They were acting in support of MGM Resorts, which owns casinos in Las Vegas and one in western Massachusetts, which could compete with the proposed new Connecticut facility.
Heller has not spoken publicly since his name was floated over the weekend.
Zinke made a mark in his two years on the job.
He led a months-long review of national monument boundaries, and the President accepted two of his recommendations to shrink protected lands.
His legacy also includes a bullish approach to US energy production, including mining and drilling.
Among his unfinished business is legislation to address billions of dollars in maintenance backlogs at national parks and other facilities run by the Interior Department.
His critics, however, see an opportunity in Zinke's departure to turn the page. His leadership "was a disaster for public lands of historic proportions," said Chris Saeger of the Western Values Project.