Since becoming the chief steward of America’s natural resources in March 2017, Zinke has been the focus of a steady drumbeat of federal investigations ― one of which was recently referred to the Department of Justice. Environmental groups have likened him to former Environmental Protection Agency Administrator Scott Pruitt, who resigned from his post in July amid a frenzy of ethical scandals.

After their victory Tuesday, House Democrats will gain powerful subpoena authority starting Jan. 3 ― and they plan to use it.

Zinke is a “target-rich environment” and there is “no question” Democrats will be looking into not only his conduct, but policy changes made at Interior under his watch, Rep. Gerry Connolly (D-Va.), the vice ranking member of the House oversight committee, told HuffPost by phone.

“Mr. Zinke is definitely going to be a subject of great interest,” Connolly said. “I think everything is potentially on the table.”

Chip Somodevilla via Getty Images Rep. Gerry Connolly (D-Va.) is a member of the House oversight committee.

Connolly’s Democratic colleague Raul Grijalva (Ariz.), one of Zinke’s most vocal critics in Congress and likely the next chairman of the House Natural Resources Committee, promised even before the midterms that if he’s given the gavel, he will call the interior secretary in to testify about his many “failures and scandals.”

In a series of posts on Medium, Democrats on the Natural Resources Committee accused their Republican colleagues of failing to conduct oversight on “the most ethically challenged member of the Trump administration.” And days before the election, they launched a new Medium series called “Watchdog,” which documents Zinke’s numerous ethical lapses.

A priority of both Grijalva and Connolly will be getting to the bottom of what Connolly called an “abortive attempt” to replace the head of Interior’s office of inspector general with a Trump political appointee from the Department of Housing and Urban Development. The OIG has several ongoing investigations into Zinke’s conduct.

The Hill first reported the shake-up in October, citing an internal email in which HUD Secretary Ben Carson announced Suzanne Israel Tufts’ departure. Two days later, Interior Department spokeswoman Heather Swift denied the story, saying the media had jumped to conclusions.

Carson’s announcement came shortly after the Interior Department’s watchdog referred one of its investigations to the DOJ, according to The Hill. That investigation was most likely one looking into Zinke’s ties to a Montana real estate development that’s backed by the chairman of oil giant Halliburton.

Tufts subsequently resigned as HUD’s assistant secretary.

Along with looking into whether Zinke has used his office for personal gain, Grijalva and Connolly plan to investigate policy decisions he and his team have made, including drastically shrinking a pair of protected national monuments in Utah. In December, on Zinke’s recommendation, Trump cut the 1.87 million-acre Grand Staircase-Escalante National Monument, the largest land national monument in the country, roughly in half. The nearby 1.35 million-acre Bears Ears National Monument was slashed by 85 percent. The moves opened the door for oil, gas and other development.

Joshua Roberts / Reuters Interior Secretary Ryan Zinke has faced at least 17 federal investigations, many of which are ongoing.

Connolly is among many lawmakers and legal experts who argue U.S. presidents don’t have the authority to abolish, shrink or otherwise weaken national monuments.

“I think that’s a live issue,” Connolly said of rolling back monument protections. “Not only looking retrospectively at what they did and questioning its legality, but prospectively. If they can do that unchallenged, that has real implications for every Antiquities Act set-aside since Teddy Roosevelt.”

Seventeen presidents, including Trump, have used the 1906 law to designate more than 150 monuments.

Other potential oversight priorities will be Interior’s sweeping proposal to open up nearly all U.S. waters to oil and gas development, Zinke’s proposed reorganization of the agency, and its decision to block two tribes’ application to open a casino in Connecticut. The casino rejection and Zinke’s influence over the shrinking of Grand Staircase-Escalante are the subject of ongoing probes by Interior’s inspector general.

Connolly said that following a “complete desert of oversight under the Republican watch” over the last two years, there’s a big appetite for looking into major rollbacks and policy changes, be they at Interior, the EPA or elsewhere. Since Trump took office, Republicans on the House oversight committee have denied more than 60 subpoena requests from Democratic members. On that list is a request for documents Interior withheld about Zinke’s reassignment of career employees.

Rep. Elijah Cummings (D-Md.), the incoming chair of the House oversight committee, said in a statement Wednesday that he plans to “shine a light on waste, fraud, and abuse in the Trump Administration.”

“I want to probe senior Administration officials across the government who have abused their positions of power and wasted taxpayer money,” he said.

The Democrats owe the considerable investigatory powers they will now look to wield against the Trump administration in part to actions taken by their political opponents. In 2015, Republicans changed rules to give numerous committee chairs the power to unilaterally issue subpoenas to force witness testimony and obtain documents. Until then, the head of the Oversight and Government Reform Committee was the only committee chair with such power.

In a February 2015 letter, Grijalva and 15 other Democrats warned that the rule changes were “an invitation to abuse.” But Grijalva thinks the interior secretary’s actions warrant serious inquiry, telling Outside Magazine and other outlets recently that he will use that subpoena power, if necessary, to obtain needed information.

It remains to be seen if Zinke keeps his job as interior chief. Politico reported last month that he is among several Cabinet members likely to leave after the midterm elections. On Wednesday, Trump told reporters that Zinke is “doing an excellent job,” but that he would “take a look” at the allegations against him and likely make a decision about his future next week.

Interior did not respond to HuffPost’s Wednesday request for comment on Democrats’ plans to put Zinke under a microscope. But agency spokeswoman Heather Swift told Politico in September that the secretary won’t be intimidated.

“In his 23 years of military service, and continued public service after that, Ryan Zinke has dealt with far more formidable opponents and never quit,” Swift said.