Mr. Zinke was considered a surprise choice for the position. He had reportedly gained favor with Donald Trump Jr., because, like the president’s son, he is an avid game hunter.
He ran the office with a swaggering flair that won him the admiration of the president and conservative Westerners, many of whom applauded his effort to move major department operations to places like Denver or Boise, Idaho. But his style also drew derision from the environmental community and the quiet mockery of many career staff members in his own agency.
In Washington, he flew a special interior secretary flag above the Interior building when he was present, and he often skipped a coat and tie for fishing shirts and boots. Beyond the capital, he hiked and rode across landscapes in a cowboy hat, even as he pushed plans to drastically reduce monument boundaries.
In June, Politico reported that Mr. Lesar, the Halliburton chairman, was lending financial backing to a major development in Mr. Zinke’s hometown, Whitefish, that would significantly raise the value of property owned by Mr. Zinke. The development would include a hotel, shops and a brewery, and Mr. Zinke’s wife had pledged in writing to allow the developer to build a parking lot that would help make the project possible. The land for the potential lot is owned by a foundation created by Mr. Zinke.
Because Halliburton is the nation’s largest oil services company, and because Mr. Zinke regulates the oil industry on public land, the deal raised questions as to whether it constituted a conflict of interest. Mr. Zinke’s schedule also showed that he had hosted Mr. Lesar and a developer involved with the hotel-brewery project in his secretarial office in 2017.
In response, three Democrats sent a letter to the Interior Department’s top watchdog, Mary L. Kendall, requesting an investigation into whether Mr. Zinke had used his position as secretary for personal financial gain. In July, Ms. Kendall complied, opening an investigation. In October, her department forwarded at least one inquiry to the Justice Department.
Heather Swift, a spokeswoman for Mr. Zinke, has said that the secretary did nothing wrong and that he resigned from his charitable foundation’s board of directors before the deal was made.