Jason Chaffetz, the Utah congressman wrapping up his first term atop the powerful House Oversight Committee, unendorsed Donald Trump weeks ago. That freed him up to prepare for something else: spending years, come January, probing the record of a President Hillary Clinton.

“It’s a target-rich environment,” the Republican said in an interview in Salt Lake City’s suburbs. “Even before we get to Day One, we’ve got two years’ worth of material already lined up. She has four years of history at the State Department, and it ain’t good.”

In a tweet Wednesday night, Chaffetz reaffirmed his distaste for Clinton and his refusal to endorse Trump — but reversed his plans not to vote for the Republican nominee.

If Republicans retain control of the House, something that GOP-friendly maps make possible even in the event of a Trump loss, Clinton will become the first president since George H.W. Bush to immediately face a House Oversight Committee controlled by the opposition party. (Bill Clinton, George W. Bush and Barack Obama lost Congress later in their presidencies.)

[House wave still looking more like a ripple for Democrats]

Former secretary of state Hillary Clinton testifies before the House Select Committee on Benghazi in October 2015. (Melina Mara/The Washington Post)

And other Republican leaders say they support Chaffetz’s efforts — raising the specter of more partisan acrimony between them and the White House for the next four years.

“The rigorous oversight conducted by House Republicans has already brought to light troubling developments in the [Hillary] Clinton email scandal,” the office of House Speaker Paul D. Ryan (R-Wis.) said in a statement to The Washington Post. “The speaker supports [Oversight’s] investigative efforts following where the evidence leads, especially where it shows the need for changes in the law.”

And the Oversight Committee may not be the only House panel ready for partisan battle. While the Select Committee on Benghazi appears to have finished its work, Rep. Jim Jordan (R-Ohio), a committee member who says Clinton might have perjured herself on questions about her email, said recently that he wants the committee to continue.

On the campaign trail, Republicans running for every office confidently talk about Clinton facing criminal charges one day.

“Lady Justice doesn’t see black or white,” Rep. Ken Buck (R-Colo.) said Wednesday at a rally in Loveland. “She doesn’t see male or female. She does’t see rich or poor. But soon, lady Justice will see Hillary Clinton.”

If she wins, Clinton would enter office with low favorability ratings and only one-third of voters considering her “honest and trustworthy.” As a result, Republicans are not inclined to give her a political honeymoon. To many of them, a Clinton victory would mean that Trump threw away an election that anyone else could have won.

“This should have been a slam dunk for the GOP,” party consultant Frank Luntz said Sunday on CBS News’s “Face the Nation.”

House Speaker Paul Ryan (R-Wis.) told Republican lawmakers on Oct. 10 that he would no longer support presidential nominee Donald Trump—the start of a messy breakup that will go on through Election Day. (Peter Stevenson/The Washington Post)

That analysis stems from the investigations Republicans have led — or asked for — into Clinton’s tenure at the State Department. Clinton has been dogged by investigations into the terrorist attacks in Benghazi, and for the better part of two years, she’s reeled from questions about the private email server she used while secretary of state. Chaffetz, too, views Clinton as a lucky candidate whose past will catch up with her after the polls close.

“She’s not getting a clean slate,” he said. “It’s not like the State Department was bending over backwards to help us understand what was going on. We’ve got document destruction. We’ve got their own rogue system. We’ve got classified information out the door. We’ve got their foundation doing who knows what. I mean, it took them four years just to release her schedule.”

Several Clinton allies recoiled when asked about Chaffetz’s plans for 2017. Clinton spokesman Brian Fallon said Chaffetz threatened to “ignore the public’s clear desire for the two parties to work together,” and he and others accused Chaffetz of wasting taxpayer money chasing old stories.

“It’s clear Congressman Chaffetz is ready to spend resources on additional worthless political investigations that will, again, come up with nothing,” said David Brock, a former Clinton foe who now runs the pro-Clinton political action committee American Bridge and its affiliates.

Rep. Elijah E. Cummings (Md.), the ranking Democrat on the Oversight Committee and the Select Committee on Benghazi, said that new Clinton investigations based on the scandals vetted since 2013 would amount to waste.

“Republicans are pretending like they haven’t been investigating Secretary Clinton for years ever since she announced that she was running for president, including everything from Benghazi to emails to the Clinton Foundation,” Cummings said in a statement. “It’s no exaggeration to say that on the first day Secretary Clinton walks into the White House, Republicans will have already investigated her more than any other president in history.”

Chaffetz, elected in 2008 after beating a congressman in a primary, rose quickly in the House. After John A. Boehner’s surprise retirement, Chaffetz briefly ran for speaker of the House. Today, he says he’s “supportive” of Ryan and has no plan to chase his job — though he does not rule out supporting someone else. Oversight, he explained, is “where the action is.”

Chaffetz emphasized that the questions raised since he took over the committee in 2015 have not all been answered.

“We still have tens of thousands of missing documents,” he said. “That ranges from everything from the missing boxes [of subpoenaed emails] to the David Petraeus emails, to [State Department Undersecretary] Patrick Kennedy’s communications.”

Chaffetz also suggested that coming Clinton hearings would touch on issues that had not been vetted. He had sent the committee’s investigators a weekend article from the Wall Street Journal that asked whether Virginia Gov. Terry McAuliffe (D) had slanted the FBI’s probe of Clinton by helping outside groups put $467,500 into the campaign of Virginia senate candidate Jill McCabe, whose husband, Andrew, later became deputy director of the FBI.

“It seems like an obscene amount of money for a losing race,” Chaffetz said. “The ties between the governor and the Clintons are well-known. He raises money for a lot of people, but why so much for this one person?”

In addition, Chaffetz previously said in an interview with CNN, an FBI agent’s suggestion that Kennedy had tried to get Clinton’s emails declassified deserved a hard look. “I honestly don’t believe they act in the best interests of our country,” he said of the State Department. Future Oversight Committee investigations, he said, might depend on whether Clinton tries to put people ensnared by previous probes into her administration.

“It depends on who stays and who goes,” Chaffetz said. “If Hillary Clinton brings in the same gang — Loretta Lynch, Cheryl Mills, Huma Abedin, Jake Sullivan — she has her cast of characters. If they put on the same play, she’s not going to get good reviews from the critics. Every single time we turn around, this puzzle gets more complicated with more pieces to it. That story about the $12 million from Morocco to the Clinton Foundation? You could take any one of these stories and have a year’s worth of investigations.”

But the Morocco story also points to a potential problem for Chaffetz. The embarrassing 2015 emails from Clinton staffers, debating whether the future candidate should go to Morocco to collect a large charitable donation, came from hacked exchanges published by WikiLeaks. Chaffetz was inclined to steer away from them and had told Oversight Committee investigators to avoid poking through the website’s cache. “You don’t want to be dealing with stolen documents,” he said.

[WikiLeaks reveals fears and frustrations inside Clinton world]

Few Republicans share that caution. At his rallies, Trump has cited several WikiLeaks-based stories and accused the media of covering them up — sometimes before leading chants of “lock her up,” directed at Clinton. He has also drawn attention to women who have accused Bill Clinton of unwanted sexual advances, and to videos produced by conservative sting artist James O’Keefe that purport to show Democratic strategists plotting violence at Trump rallies.

Rep. Tim Murphy (R-Pa.), who chairs the investigative subcommittee of the Energy and Commerce Committee, tweeted that he was “stunned” by the O’Keefe videos. Chaffetz did not mention them. While Democrats blanch at what he might investigate, Clinton’s longtime critics worry that the Oversight Committee will not go far enough.

“In the past, Republicans have used scandal investigations to keep their political opponents off kilter, as opposed to using them for serious accountability,” said Tom Fitton, the president of Judicial Watch, which has filed dozens of ongoing Clinton suits. “They made noise about Clinton lying to Congress, when, if they were really concerned about it, they could have passed a contempt resolution.”

The negative feelings toward Clinton — the certainty, in conservative media, that she is “crooked” — could put pressure on Republicans from the first moments of Clinton’s presidency. Asked whether investigations could lead to extended political crises, with echoes of Watergate, Chaffetz said it would depend on Clinton and her team.

“It depends on how cooperative they are, how seriously they take it,” Chaffetz said. “If they continue to erect walls and shore up the turrets, then, yeah, it’s going to be a battle. But if they act like they’re supposed to, if they comply with subpoenas and actually respond to requests from Congress, well, our republic requires that.”

The one thing Chaffetz will not consider is an election that goes badly against the GOP. He sees the Oversight Committee as “the tip of the spear,” with a valuable role to play in challenging the executive. If Republicans lose the majority, Chaffetz has no Plan B.

“Heaven help us!” said Chaffetz, laughing. “Please, no! I’m not even going to think about that one. I can’t even utter the sentence out loud.”