WASHINGTON — Several key players in the House impeachment inquiry of President Donald Trump were the strongest proponents of Republicans’ iron-fisted oversight of the Obama administration, culminating in a two-year House probe of 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 of Ohio, who is the top Republican on the House Oversight Committee. The panel’s chairman, then-Rep. Trey Gowdy of South Carolina, who has since left Congress, will serve as an outside lawyer for Trump.

“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 Holder in contempt for not cooperating with its probe of a botched gun-walking 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 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 GOP’s 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 Republican-led 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 didn’t 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.

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 House Majority Leader Kevin McCarthy of California credited the panel with lowering Clinton’s approval ratings.

One Republican who served on the Benghazi panel and has since retired, Lynn 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.”

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.