Every few weeks, Donald Trump and his Republican allies in Congress claim they’ve found something that will prove the Russia investigation was a sham—a “witch hunt,” in the president’s words—all along. Conservative media outlets build a steady drumbeat of hype, telling their audience that this is the proof they’ve been waiting for. Ultimately, in every instance, their claims fall far short.

That track record makes it impossible to take the latest round of allegations at face value. In recent days, House Republicans have been pressuring the Justice Department to disclose information about someone inside the Trump campaign who clandestinely shared information with the FBI during the 2016 election. Those efforts received a White House endorsement on Thursday when President Donald Trump tweeted about an “embedded informant” inside his campaign.

McCarthy, a National Review contributing editor and a former federal prosecutor, is one of the conservative legal world’s most prominent skeptics of the Russia investigation. In a May 12 column, “Did the FBI Have a Spy in the Trump Campaign?,” McCarthy pointed to congressional testimony last August by Glenn Simpson, the co-founder of opposition research firm Fusion GPS. Simpson told lawmakers that Christopher Steele, the British ex-spy whom Fusion hired to dig up dirt on Trump, had told him that the FBI took Steele’s dossier seriously because the bureau “had other intelligence about this matter from an internal Trump campaign source.”

The New York Times confirmed the existence of an informant—not a spy, which is different—in an article on Wednesday about the origins of the Russia investigation: “The F.B.I. obtained phone records and other documents using national security letters—a secret type of subpoena—officials said. And at least one government informant met several times with” Trump campaign aides Carter Page and George Papadopoulos. The article prompted conservatives, including Trump lawyer Rudy Giuliani, to return to the issue.

This, in turn, fueled further tweets from Trump on the subject on Friday:

Generally speaking, there’s nothing unusual about federal investigators using informants in a major criminal and counterintelligence case. Giuliani, who once led the federal prosecutors’ office in Manhattan, should be well aware of their importance and ubiquity when taking down organized-crime figures and white-collar criminals. The lure of witness-protection programs and immunity from prosecution helped Giuliani’s office rack up numerous convictions against New York’s Five Families in the 1980s, for example.

The fact that someone associated with Trump’s campaign felt the need to secretly cooperate with the FBI would seem to reflect negatively on the campaign above all. But in the Trump team’s version of events, the real scandal is the FBI’s behavior, not theirs. “Why would they be there?” White House staffer Kellyanne Conway asked in a CNN interview. Fox News legal analyst Gregg Jarrett told Sean Hannity on Thursday night that the revelations proved that the FBI was out to get Trump from the start.

“The use of this confidential informant by Comey and his minions of the FBI should erase any doubt ... that this is an agency of the government that abused its power in an attempt to frame Donald Trump and destroy him,” Jarrett said. “They were trying to entrap people in the Trump campaign to say something incriminating and, of course, they were never charged with collusion so they said nothing of the sort.” Hannity, who is reportedly one of Trump’s closest advisers, added in agreement, “Collusion is not a crime.”

Granted, it would be deeply disturbing if today’s FBI routinely sought out informants in American political organizations or placed their own agents inside them. There’s a dark history behind these fears: Under J. Edgar Hoover, the bureau successfully infiltrated the civil-rights movement and other political organizations it deemed to be “subversive.” The FBI largely abandoned these practices in the post-Watergate era, though echoes of the past still emerge.

But there’s no evidence so far that federal investigators have undertaken any sort of Stasi-like operation here. If anything, there was more than enough smoke emanating from the Trump campaign in 2016 to justify the FBI’s concern about an actual fire: questions about campaign aide Paul Manafort’s ties to Putin-linked parties in Ukraine, Page’s summer sojourn to Moscow, and Papadopoulos’s loose-lipped chat with an Australian diplomat about potential Kremlin dirt on Hillary Clinton, for example.

Based on what’s known so far, what’s most disturbing is the pattern of behavior from Trump and congressional Republicans over the past year. It began last March when California Representative Devin Nunes held a strange White House press conference to claim there was proof to support Trump’s allegations that Barack Obama had wiretapped Trump Tower. The stunt by Nunes, who leads the House Intelligence Committee, marked the beginning of a long, damaging road for the oversight body’s credibility. Six months later, the Justice Department later told a federal court that no such evidence existed.

Then came the texts between FBI employees Peter Strzok and Lisa Page, which were discovered by the FBI’s inspector general last summer and later selectively leaked by members of Congress. Conservatives pointed to texts that disparaged Trump during his candidacy as evidence of the FBI’s institutional bias. By the time the candid exchanges became public, however, Mueller had already removed Strzok from his team because the inspector general had notified him of the texts’ existence. The messages also included criticism of Democratic figures like Chelsea Clinton, Bernie Sanders, and former attorney general Eric Holder, undercutting conservatives’ narrative.

In January, Republicans on the House Intelligence Committee began to demand the release of a classified memo they had drafted that purported to describe abuses of the FISA process. The Nunes memo, as it came to be known, claimed that FBI and Justice Department officials used “politically motivated or questionable sources” to obtain a surveillance warrant against Page during the 2016 election. Nunes and other top Republicans defended the memo as part of their oversight functions for the nation’s vast intelligence apparatus.

But it was also clear that Republicans sought to undermine the Russia investigation and insulate Trump from further political damage. The Justice Department called the memo’s impending release “reckless” and the FBI issued an unusual public statement warning that the bureau had “grave concerns about material omissions of fact that fundamentally impact the memo’s accuracy.” Trump eventually approved its release after some redactions. The memo’s contents not only fell far short of Republicans’ hype, but bolstered the investigation’s credibility in some ways.

Now it’s reports of an informant inside the Trump campaign, and the president’s “allies are waging an increasingly aggressive campaign to undercut the Russia investigation by exposing the role” of the informant, the Post reported on Thursday. (The article notes that the source “is a U.S. citizen who has provided information over the years to both the FBI and the CIA ... and aided the Russia investigation both before and after Mueller’s appointment in May 2017, according to people familiar with his activities.” CNN reported on Friday that the source was not, to use Trump’s malapropism, “implanted” in the campaign by the FBI.)

Once again, there’s a strong pushback from FBI and Justice Department leadership. “The day that we can’t protect human sources is the day the American people start becoming less safe,” FBI Director Christopher Wray told senators earlier this week. “Human sources in particular who put themselves at great risk to work with us and with our foreign partners have to be able to trust that we’re going to protect their identities and in many cases their lives and the lives of their families.”

It’s worth noting that the redacted Nunes memo, perhaps for the very reason that it was redacted, didn’t do the damage that federal law-enforcement officials had warned about. But it’s easy to see how the outing of an FBI informant—especially for nakedly partisan reasons, a true “witch hunt” of sorts—would be disastrous for the bureau’s ability to investigate criminal conspiracies, to say nothing of the informant’s safety. For most Americans, that would be enough reason for caution. For Trump and his allies, it may be an incentive to push harder.