Remember the great “unmasking scandal” of 2017?

Maybe not. But for a hot minute last year,  defenders of President Trump were screaming to the skies, claiming to have found proof that the Obama administration had used the nation’s intelligence-gathering powers to spy illegally on the Trump campaign.

The “mastermind” behind that claim, House Intelligence Chairman Devin Nunes, held a dramatic press conference to announce that he was immediately taking the evidence to the White House to personally brief the president. Trump himself would later embrace and expand the claim, calling it just “just the tip of the iceberg” of the conspiracy against him. Conservative media also huffed itself into full outrage mode, with outlets such as National Review comparing it to Watergate and Fox News reporting that a “smoking gun” had been found to prove the allegations, with criminal charges almost certain to follow.

And then, nothing.

All it took was a cursory examination of the evidence -- the kind of thing that any responsible person would conduct before making such explosive public claims -- to determine that the whole thing had been a baseless sham invented by Nunes to try to protect Trump, distract voters and to try to discredit the Russia investigation.

But if Nunes is not too bright or ethical, he is certainly diligent. That fake scandal was quickly followed by another, this time over the so-called Nunes memo. In that memo, the California congressman claimed to have compiled classified information proving the existence of an anti-Trump cabal within the FBI that had abused its powers in investigating the president. Once again, the conservative noise machine revved itself up; once again, Trump joined the fray, clearing the way to have the Nunes memo declassified and telling aides that it would prove his claim of a witch hunt against him.

Yet when the ballyhooed memo was made public, it too proved to be nonsense, making far-fetched claims that it could not corroborate with facts. At least some Republicans who had championed its release turned sheepish at their role in the controversy.

Undeterred, Nunes went at it yet again, this time demanding that the Department of Justice release a top-secret wiretap warrant sought and obtained by the FBI against Carter Page, a former Trump aide who had long been suspected of acting as a Russian agent. Nunes and others claimed that the warrant’s release would prove that the FBI had acted criminally by deceiving federal judges to obtain the warrant.

When the DOJ balked at declassifying the warrant, pointing out the dangers of releasing such documents in the midst of an ongoing investigation, Nunes and his supporters cited that reluctance as evidence of a coverup. Once again, the Hannity types flew into high dudgeon. Once again, extravagant claims were made. Once again, Nunes eventually got his way, forcing the release of the warrant.

Once again, when the document was declassified, it proved that his charges had been groundless.

That’s three times in a row, and now we’re on to Number Four, the most dangerous of them all.

This time, Nunes is demanding that the DOJ hand over secret information containing the identity of someone described as a longtime CIA and FBI confidential source who may have had contacts with Page and George Papadopoulus. Once again, the claim is that the existence of this person would somehow prove an FBI conspiracy against Trump.

Once again, Trump is an eager participant:

As Trump was sending these tweets, his attorney, Rudy Giuiliani, was on national TV admitting that neither he nor the president even know whether this informant exists. In other words, Trump is putting not just his personal reputation, but the reputation, authority and gravitas of the president of the United States behind this conspiratorial nonsense with no idea whatsoever as to its validity. At any other time, under any other president, this kind of irresponsibility would be unthinkable. Under Trump, it has become commonplace.

So far, FBI and DOJ officials have been adamant about not releasing any information that might reveal the name of an informant to a Congress with a less-than-stellar record of keeping secrets. And despite Trump’s description of this as a conspiracy by the “Obama FBI,” the pushback is being led by officials that were appointed by Trump himself.

“As anybody in the intelligence community knows, human sources in particular who put themselves at great risk to work with us and with our foreign partners have to be able trust that we’re going to protect their identities and, in many cases, their lives and lives of their families,” FBI Director Christopher Wray told Congress Wednesday. “And the day that we can’t protect human sources is the day the American people start becoming less safe.”

If this person exists, Wray knows who it is. If he has the slightest concern of anything improper in the investigation before he took office, he would undoubtedly intervene.  He has not.

So if Trump nonetheless pushes the release of that information, I could easily envision it leading to resignations at the FBI and the Department of Justice, with top officials concluding that they cannot in good conscience participate in the exposure of sources to whom they have pledged confidentiality, particularly when the motivations are so blatantly partisan.

Even if this informant does exist, the description of him or her as a “spy” “embedded” for “political purposes” is bizarre. The FBI had clear cause to fear Russian intervention into our elections, and also to suspect that Russia may have attempted to infiltrate the Trump camp. They weren’t seeking information on the campaign’s inner workings so they could leak it to the Clinton campaign, they were investigating a potential national security threat. Using informants and whistleblowers is a perfectly normal investigative technique in such cases.

Two final points:

-- How many times does Nunes have to lead his fellow conservatives down the rabbit hole before they refuse to follow him down the next one? At some point, doesn’t it get embarrassing? Doesn’t a basic instinct to preserve a modicum of self-respect kick in at some point?

-- If Trump is innocent, why doesn’t he act like it? Stop signing onto half-baked conspiracy theories, shut your mouth, do your job, give the special counsel the documents that he requests, and when the time comes, answer his questions. The only reason the Mueller investigation is in the news on an almost hourly basis is because Trump and his defenders put it in the news, trying desperately to turn a legal case they fear they can’t win into a public-relations battle they hope they can.