Several key players in the House impeachment inquiry of President Trump were the strongest proponents of Republicans’ iron-fisted oversight of the Obama administration, culminating in a two-year House probe into the deadly 2012 terrorist attacks in Benghazi, Libya.

Now, faced with a politically charged investigation into a president of their own party, they have dropped their formerly stout defense of congressional prerogatives and have joined Trump in endorsing a campaign of massive resistance to the impeachment probe — a turnabout that has left many Democrats and even some Republicans aghast.

Among those who participated in the select committee that probed the attacks on U.S. facilities in Libya were Mike Pompeo, then a Kansas congressman and now secretary of state and a key target of the current Democratic investigation, and Rep. Jim Jordan (Ohio), who is the top Republican on the House Oversight Committee. The panel’s chairman, then-Rep. Trey Gowdy (S.C.), who has since left Congress, was poised to serve as an outside lawyer for Trump. The president said Thursday that Gowdy would have to wait until January to start due to lobbying rules.

Top moments from the first leg of the House Select Committee hearing on Benghazi where former secretary of state Hillary Clinton testified in October 2015. (Sarah Parnass/The Washington Post)

“The notion that you can withhold information and documents from Congress no matter whether you are the party in power or not in power is wrong,” Gowdy said in 2012, as a House panel moved to hold then-Attorney General Eric H. Holder Jr. in contempt for failing to cooperate with its probe of a botched gunrunning operation. “Respect for the rule of law must mean something, irrespective of the vicissitudes of political cycles.”

Gowdy did not respond to requests for comment but criticized the House investigation last week in Fox News Channel appearances — calling its leader, House Intelligence Committee Chairman Adam B. Schiff (D-Calif.), “deeply partisan” and accusing him of leaking information “like a sieve.”

In a 2016 addendum to the House Benghazi probe’s findings, Pompeo and Jordan thrashed Democrats, saying they “showed little interest in seeking the truth” and “spent the bulk of their time trying to discredit the Republican-led committee and leveling baseless personal attacks.” But in past weeks, the two have used similar tactics to undermine the House impeachment probe by, in Pompeo’s case, accusing Democrats of “bullying and intimidating State Department employees” in justifying a decision to block testimony and, in Jordan’s case, accusing the probe’s leader of misconduct and disqualifying political bias.

“There is obviously a massive hypocrisy here,” said Jen Psaki, an Obama administration veteran who served as State Department spokeswoman during the Benghazi probe.

Pompeo, she added, “was one of the ringleaders of a massive political circus around Benghazi; he was responsible for dragging countless Foreign Service officers, civil servants — people who had been serving Democrats and Republicans for decades — in front of Congress, through the mud. Now he’s claiming that he’s defending the institution? That irony is not lost.”

The State Department had no immediate comment.

The Republicans’ fealty to Trump just a few years after their steadfast defense of congressional oversight has cast a spotlight on their words and actions in the Benghazi probe as well as GOP investigations into the Justice Department and the Internal Revenue Service.

Those probes uncovered serious lapses inside the government that led to grave and sometimes deadly consequences, but they did not reveal misconduct at the highest levels of the Obama administration, as many Republicans had suggested they would. And while Republicans tussled with the White House for months over access to evidence, they ultimately obtained tens of thousands of pages of documents and dozens of witnesses for each probe.

The Benghazi probe culminated in an 11-hour October 2015 hearing featuring former secretary of state and presidential candidate Hillary Clinton, a made-for-TV spectacle that failed to elicit significant new information about the attacks that killed four Americans, including U.S. Ambassador Chris Stevens.

The Trump administration has thus far refused to cooperate in any way with the impeachment investigation after months of stonewalling other probes launched by House Democrats.

Experts are warning of a potential breakdown of the constitutional checks and balances on the presidency if the bipartisan consensus on executive oversight is eroded.

“We’ve always had a system of government in which there were houses of Congress and committees of Congress where the majority and minority simultaneously looked after their own interests yet cooperated with each other,” said Charles Tiefer, a University of Baltimore law professor who served as Democratic counsel on several high-profile congressional investigations. “If we have a situation where the president can command noncooperation, he will effectively shut down the system of checks and balances.”

He added, “We could have presidential abuses in the future that would make what [Richard] Nixon did look like finger-painting in a nursery school.”

Democrats viewed the appointment of a special Benghazi committee in 2014 as a political witch hunt aimed at damaging Clinton, and they debated whether to even participate after five other House committees had already reviewed the episode. Those suspicions were borne out the next year when then-House Majority Leader Kevin McCarthy (Calif.) credited the panel with lowering Clinton’s approval ratings.

One Republican who served on the Benghazi panel and has since retired, Lynn A. Westmoreland of Georgia, argued that the situations are “different” because the panel was investigating an event rather than a person. And despite the ultimate scale of cooperation — running to 107 witnesses and more than 100,000 pages of documents by the panel’s own statistics — Westmoreland maintained that “Obama stonewalled” the Benghazi investigation.

“We were just trying to investigate what happened,” he said. “There wouldn’t have been any criminal charges. I don’t think there would have been any consequence to anybody for any of their testimony.”

Westmoreland also argued — as have Gowdy, Jordan and Pompeo, as well as the Trump administration — that Democrats are upending precedent and sidelining Republicans by moving for a lightning-fast impeachment: “I just have a problem with the fact that it just doesn’t seem like they’re following the process. And when you have a bad process, you have a flawed product.”

Jordan was not available for an interview but told reporters Monday that he agreed with the Trump administration’s decision, later detailed in a letter, not to cooperate because of the “illegitimate” nature of the impeachment probe.

“If it’s going to be this kind of process . . . we understand why they made this decision at this moment,” Jordan told reporters Monday after a State Department official, Gordon Sondland, failed to appear for a House deposition.

Jordan spokesman Russell Dye said the deliberate nature of the Benghazi probe stood in contrast to the pace of the House impeachment probe: “Gowdy went slow. You have to contrast that with Nancy Pelosi saying you have to ‘strike while the iron is hot,’” Dye said, referring to comments made by the House speaker. “Nobody can look at how this is going and say there is strategy, deliberation or investigative force that would lead to serious fact-finding.”

But it remains unclear if the White House would cooperate with the impeachment investigation even if the House took a formal vote authorizing one, as Republicans are demanding, and there are a wealth of instances where Trump’s defenders lambasted the White House for refusing to comply with Congress.

“The only route to the truth is through the House of Representatives,” Jordan said in 2014, as the House voted to hold IRS official Lois Lerner in contempt of Congress for declining to answer lawmakers’ questions about allegations of political bias in the handling of tax exemptions for nonprofit groups.

Another Republican close with the Benghazi investigation who spoke on the condition of anonymity to speak frankly called the turnabout “just part of the irony of the inevitable twists and turns of Washington, in that different people are playing different hands and different roles.”

The investigator compared the situation to the about-face former congressman Mick Mulvaney (S.C.) did when he joined the Trump administration as budget director: Famous for his refusal to raise the debt ceiling when he was in Congress, Mulvaney asked his former GOP colleagues to do just that after assuming his new role in 2017.

Kurt Bardella, a former spokesman and senior adviser for Republicans on the House Oversight Committee who is now an outspoken critic of Trump and his GOP supporters, called the oversight turnabout “a complete betrayal of everything that they claimed to stand for during the Obama years,” and said Democrats should stand ready to confront Trump’s congressional allies with their own words.

“I think that they should be challenged to explain what’s different now versus then,” he said. “Why have they done a complete 180? They had no issues with cooperating and subpoenas when they were the ones issuing them.”