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WASHINGTON — President Donald Trump says he's nominating a Washington veteran with lobbying ties to U.S. energy companies to lead the Interior Department.

David Bernhardt, currently Interior's acting head, would replace Ryan Zinke if the Senate approves his nomination. Zinke resigned in December amid ethics investigations.

Trump tweeted Monday that Bernhardt "has done a fantastic job from the day he arrived."

The Colorado native first served in the department under President George W. Bush. He had been a deputy under Zinke.

Bernhardt also worked as a lobbyist and lawyer for several oil and gas companies and other interests that sometimes have regulatory matters before the department.

Republicans say Bernhardt's revolving-door experience makes him an informed regulator in matters before the agency. Democrats and environmental groups say he's vulnerable to conflicts of interest.

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In order to do his current job at Interior, Bernhardt has an ethics recusal naming 26 different entities or people that are off limits. And not all of Bernhardt's former clients made it to the recusal form.

Clients from earlier years such as the Arizona-based private equity firm Diamond Ventures, the Navajo Nation and Vail Resorts Management were not deemed to be recusal worthy.

One recent client that did not make the recusal list is the foundation for Safari Club International. The pro-hunting organization is listed on Bernhardt's financial disclosure as a former client. Safari Club lobbies the Interior Department on endangered species issues and trophy hunting, according to lobbying disclosures.

Few people know ethics rules at Interior as well as Bernhardt, since he used to be the chief ethics officer at the agency under Bush.

"Upon arrival at Interior, Mr. Bernhardt, who is meticulous regarding his ethical compliance, sat down with Interior career ethics officials and walked through his entire former client portfolio and financial interests," said Interior spokesperson Faith Vandervoort in an emailed statement to NBC News.

"Those professionals developed his recusal based upon their professional experience and judgment in full compliance with the law. Mr. Bernhardt has followed all of the directives to the letter and continues to consult with the ethics department on an ongoing basis," she wrote.

By August, Bernhardt's recusals won't matter. According to his ethics agreement they all expire by August 3, 2019.

In Bernhardt's current role as Acting Secretary of the Interior, he was one of the lobbying targets of his old boss, former Interior Secretary Gale Norton, who used to lobby at Bernhardt's old firm and now lobbies for MGM International. The casino giant has been pushing Interior to continue to block a tribal casino from being built in Connecticut, a matter that is now under investigation by the agency's internal watchdog.

Bernhardt also served as a board member of a small California based non-profit that has filed at least three lawsuits on endangered species matters. The organization, Center for Environmental Science Accuracy and Reliability, lists its purpose in tax filings as bringing "scientific rigor to regulatory statutes and to ensure consistent application of these statutes throughout all industries and all sectors."

Leaders in a California effort to protect salmon say Bernhardt is knowledgeable at how to skirt endangered species regulations.

"When the federal government required protections for species, including salmon, from the damage done by diverting water from nature to the desert growers, it was Bernhardt who went to court to get those protections overturned," said John McManus, president of the Golden Gate Salmon Association.