In the 1960s and 1970s, the American right set about undermining trust in the mainstream media, which it saw as dangerously infected with liberal assumptions. Later, in debates over evolution and the environment, some on the right attacked the validity of modern science. By the turn of the millennium, it was an article of faith among conservative ideologues that whole realms of human expertise were in fact intricate structures of propaganda that trapped the unwary in a matrix of deceit.

In an invaluable 2017 Vox essay titled “Donald Trump and the Rise of Tribal Epistemology,” David Roberts quoted a 2009 Rush Limbaugh rant: “Science has been corrupted. We know the media has been corrupted for a long time. Academia has been corrupted. None of what they do is real. It’s all lies!” With Trump, this ethos reached the White House. And now, to protect Trump, the right has expanded its war on empiricism to that most conservative of institutions, the F.B.I.

That’s the best way to understand the farce surrounding the infamous classified memo written by aides to Representative Devin Nunes, the Republican chairman of the House Intelligence Committee, which Trump reportedly believes will help discredit the Russia investigation. The events involved in the creation of this memo, and the multifront political battle over efforts to make it public, are so absurd and convoluted that they’re difficult to summarize, and in some ways that’s the point.

In their attempts to undermine the Russia probe, Republicans aren’t presenting a coherent theory — even a coherent conspiracy theory. They’re just sowing confusion and distrust toward the nation’s premier law enforcement agency in order to protect the president. In December, conservative columnist Kurt Schlichter wrote that, under the influence of the “poisonous” liberal establishment, the once-proud F.B.I. had become “just another suppurating bureaucratic pustule.” That’s exactly how Nunes is treating it.