The only mystery that still surrounds the “Nunes memo” — concocted by Republicans on the House Intelligence Committee and named for its chairman Devin Nunes — is why Congressional Republicans and President Trump authorized its release with such maniacal hype.

Promoted as proof of a scandal “far worse than Watergate,” in the feverish phrasing of Fox News host Sean Hannity, the document is a comical historic dud. Its four pages not only fail to discredit the special counsel investigation but only seem to bolster its importance.

All the controversy over the Nunes memo has achieved so far is to undermine Congressional oversight of the intelligence community; harm the relationship between the FBI and the White House; and wreak untold damage upon the morale of the nation’s chief bulwark against espionage and terrorism.

The humiliation of Nunes and his committee colleagues — already badly embarrassed by his attempt to show that President Obama “wiretapped” Trump Tower — is now complete. And the Russian autocrats, whose social media machinery has pushed the GOP’s #releasethememo campaign, must be laughing hardest.

So what does the memo prove? Certainly nothing that protects Trump. (Knowing his work habits, I suspect he hasn’t bothered to read it himself. He’d rather listen to Hannity talk about it.)

Let’s begin with the Republican narrative that the Nunes memo was supposed to confirm. According to the GOP version, FBI and Justice Department officials premised the Russia investigation on a tainted partisan source — the so-called “Steele dossier” put together by a former British intelligence agent for Trump opponents, including the Democratic National Committee. They allegedly further poisoned the investigative process when they obtained a warrant on Carter Page, a Trump foreign policy adviser with Russian connections, under the Foreign Intelligence Surveillance Act (FISA).

As FBI Director Christopher Ray and other knowledgeable officials noted, the Nunes memo omits many essential facts that contradict the Republican narrative. Yet even in the absence of a counter-memo prepared by Democrats on the House Intelligence Committee, which the Republicans succeeded in suppressing temporarily, it contains a telltale sentence on the final page.

Discussing the FBI’s FISA application on Carter Page, which must be approved by a special court, the Nunes memo mentions that the application cited “information regarding fellow Trump campaign advisor George Papadopoulos.”

This “information” was the fact, first reported by the New York Times, that Papadopoulos had disclosed to an Australian official the Trump campaign’s awareness of “dirt” on Hillary Clinton obtained by the Kremlin. Subsequently, Australian intelligence authorities conveyed that disturbing episode to the FBI. The Nunes memo then offers this devastating acknowledgment about the origin of the Russia investigation:

The Papadopoulos information triggered the opening of an FBI counterintelligence investigation in late July 2016 by FBI agent Peter Strzok.

In other words, the Russia probe did not originate with the Steele dossier, as claimed by countless fakers and frauds in the right-wing media and on Capitol Hill.

Equally ruinous to the Republican narrative is what the Nunes memo omits from its tendentious bullet points. Evidently the authors were foolish enough to believe that if they left salient facts out of their document, nobody would ever know. But that isn’t how democratic debate works.

For instance, the memo simply ignores the basic fact that Carter Page has been a subject of interest to the FBI’s counterintelligence division since 2013, when he turned up in an investigation of a Russian spy ring. Although Page was not indicted in that case, which led to the imprisonment of one Russian agent and the expulsion of two confederates, the FBI warned him that he had been a recruitment target.

So the legal basis for investigating Page had been established years before he met Donald Trump, let alone played a role in Trump’s presidential campaign. Indeed, the Trump campaign and the White House have repeatedly minimized Page’s participation in the campaign, presumably as part of the overall cover-up.

As the Democrats explained in a press release that summarized parts of their counter-memo:

The premise of the Nunes memo is that the FBI and DOJ corruptly sought a FISA warrant on a former Trump campaign foreign policy adviser, Carter Page, and deliberately misled the court as part of a systematic abuse of the FISA process. As the Minority memo makes clear, none of this is true. The FBI had good reason to be concerned about Carter Page and would have been derelict in its responsibility to protect the country had it not sought a FISA warrant.

Moreover, the memo’s misleading assertions are sure to instigate the release of additional information that belies its content and exposes its authors. Consider its claim concerning the sealed testimony of Andrew McCabe, the former deputy director of the FBI who left the bureau this week under pressure from the White House. He supposedly testified that the Carter Page FISA warrant would not have been issued without the inclusion of the Steele dossier.

But Democratic members of the House Intelligence Committee, who were present for McCabe’s testimony, say that badly misrepresents what he said. One way or another, the McCabe transcript will be released — and that is very unlikely to support the Republican argument.

In coming days we will learn more about the Nunes memo, its fallacies and falsehoods, especially when the answer prepared by the competent Democrats on the intelligence committee is finally released. We may discover why the FISA court renewed the FISA warrant on Page more than once — which would not have occurred if the surveillance of Page had produced nothing of concern. Both Page and his patrons may well find themselves regretting that they opened this Pandora’s box.

The first time that the White House depended on protection by Devin Nunes quickly turned into a disaster. The second time is proving their bad faith, dishonesty, and incompetence beyond a reasonable doubt.

PHOTO: Rep. Devin Nunes (R-CA) talks to reporters as he walks in the U.S. Capitol in Washington, October 15, 2013. REUTERS/Jonathan Ernst