Feds claim vaguely to know a lot about President Donald Trump’s secret Kremlin ties. What’s behind the spy mystery here? How much does the FBI know and how does it know it? At last, we have more than hints.

Ignominiously firing Andrew McCabe, the FBI’s deputy director, on January 29, 2018, just 26 hours shy of his retirement, was one of Donald Trump’s more consequential missteps. Kicking the career G-Man out of the Bureau a day short of his pension guaranteed that McCabe would seek payback, and he has gotten it mightily.

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McCabe’s memoir, out this month, has shot to the top of bestseller lists, thanks in part to President Trump’s public berating of the author. As is his custom, Trump’s hysterical tweets about the book have significantly boosted sales. Most recently, Trump’s insult that McCabe is a “poor man’s J. Edgar Hoover” got the reply, “I don’t even know what that means.” Really, none of us do at this point.

Trump seems unhinged by all the publicity McCabe’s been getting on his book tour, while the former FBI bigwig’s comments can’t sit well at the White House. McCabe has made clear that the Bureau investigated the president’s Kremlin connections because Trump so frequently parroted Russian propaganda in the Oval Office. In slightly more guarded language, McCabe stated, “I think it’s possible” when asked point-blank if President Trump might be an asset of Russian intelligence.

How exactly top counterintelligence officials in our nation’s capital came to the shocking conclusion that Donald Trump really might be working for the Kremlin is the big question lurking at the heart of the entire Department of Justice investigation into the current administration. Answering that will reveal the core secrets of this presidency and perhaps change American politics forever.

It’s no secret that senior FBI officials knew that something was amiss with candidate Trump and his foreign linkages back in 2016. That summer, the Bureau opened a tightly compartmented counterintelligence investigation into possible Russian espionage connections to Team Trump. Memorably termed CROSSFIRE HURRICANE, that inquiry opened the door to the Special Counsel investigation headed by Robert S. Mueller, III, still in progress today. What exactly the FBI’s initial investigation uncovered remains shrouded behind classification, but we’ve now gotten a big hint about what was really happening that fateful summer.

Like so much of what’s been publicly revealed about CROSSFIRE HURRICANE, it involves Peter Strzok and Lisa Page, who back in 2016 were the FBI’s counterintelligence boss and a Bureau attorney, respectively, who were also secret lovers. They exchanged a lot of indiscreet text messages about Trump during the presidential campaign, some of which had no business being in unclassified messages. For their indiscretions, Strzok and Page were run out of the FBI in disgrace, becoming something of an obsession for Team Trump, including the president himself.

Now The Daily Caller has reported what Strzok and Page told Congress last year, in closed testimony, about what was going on with CROSSFIRE HURRICANE back in mid-2016. To make a long spy story short, the lovers were concerned that mounting a serious, sustained counterintelligence investigation into Trump’s ties to Moscow ran the risk of exposing a longtime Bureau intelligence source of great value.

As Page told Congress on July 13, 2018, “If [Trump] is not going to be president, then we don’t need to burn longstanding sources and risk sort of the loss of future investigative outlets, not in this case, but in other Russia-related matters.” Two weeks later, Strzok told Congress that a notorious text exchange with his mistress about a mysterious FBI “insurance policy” actually referred to this shadowy “very sensitive source” who, The Daily Caller noted, “had provided evidence of possible collusion between the Trump campaign and Russia.”

On July 12, 2018, Strzok touched on this sensitive source in his public Congressional testimony:

What we had before us was an allegation that something significant, that members of the Trump campaign may have been working in cooperation with the Russians. Some people were saying, ‘hey look, this sensitive source of information that’s so sensitive, so vulnerable, we shouldn’t put it in danger,’ because sometimes if you go out and do aggressive investigation, if it’s a drug snitch or an intelligence source, you can cause significant harm.

Who, then, was this super-sensitive source providing the FBI with evidence of possible collusion between candidate Trump and the Kremlin? Three individuals are known to have provided information to CROSSFIRE HURRICANE: Alexander Downer, Australia’s high commissioner (i.e., ambassador to Britain), retired British spy Christopher Steele (complier of the notorious dossier about Trump and the Russians), and Stefan Halper, an academic and supposed intelligence source for the FBI and CIA.

To be blunt, none of these men is a plausible fit for the “very sensitive source” whom Strzok referenced. Downer and Halper are mere casual sources, no more than access agents, while Steele’s relationship to CROSSFIRE HURRICANE was already exposed long before Strzok and Page testified before Congress.

The clear implication of what The Daily Caller uncovered is that the FBI had a highly important intelligence source in or near the Trump campaign. In other words, the Bureau had a mole. Protecting that source was deemed more important in the summer of 2016 than stopping the Trump campaign, which the FBI knew or at least strongly suspected was in bed with Vladimir Putin.

Who could be that important to the Bureau? Logic and counterintelligence experience dictate that such a source had to be very close to Donald Trump. The mole’s identity has not been revealed and probably won’t be anytime soon, leaving major questions unanswered about how the FBI knew what it knew back in 2016—all of which is surely known to Team Mueller now.

But what if the mole wasn’t a person? The FBI has long protected super-secret technical intelligence programs, above all signals intelligence, by masquerading their information as coming from (non-existent) human sources. Were Strzok and Page obliquely referring to top-secret-plus SIGINT regarding Trump’s clandestine ties to Moscow?

That would fit with what this column previously reported about the president’s Kremlin ties. As I told you last May, “The counterintelligence investigation of Donald Trump was kicked off by not one, not two, but multiple SIGINT reports which set off alarm bells inside our Intelligence Community,” explaining that the initial information came from foreign intelligence partners. I added:

NSA understood quite a bit about Trump’s connections to Moscow, and by mid-2016, it had increased its efforts to get to the bottom of the mystery regarding the candidate’s Russian ties. In response to urgent FBI requests for more information, NSA rose to the occasion, and by the time that Donald Trump officially accepted the Republican nomination in mid-July 2016, ‘We knew we had a Russian agent on our hands,’ as a senior NSA official put it to me recently.

That seems to be the same intelligence which Strzok and Page referred to in coded language, for classification reasons. The Trump White House now is no doubt searching frantically for an FBI mole in their ranks who may not exist. Excellent technical intelligence was always the underpinning of CROSSFIRE HURRICANE, as the FBI has been careful to conceal in order to protect top-secret intelligence sources and methods. The full spy story here, just as with the last major league joint NSA-FBI counterintelligence coup against Moscow, will take decades to be fully revealed to the public.