I don’t claim to understand the whole story. But one thing is clear: The Orwellification of the G.O.P. didn’t start with Trump. On the contrary, the party has been moving in that direction for years; the mind-set Trump is exploiting was already well in place before he burst on the scene.

Consider the claims of Trump and his allies that evidence of his collusion with Russia — not “alleged” collusion, because there is no longer any real doubt — is a hoax perpetrated by the “deep state.” Where have we seen something like that before? In Republican attacks on the evidence for climate change.

Fifteen years have passed since Senator James Inhofe suggested that global warming is “the greatest hoax ever perpetrated on the American people.” This was and is an even crazier claim than the assertion of Trump and company that all of the tweeter in chief’s woes are the product of a vast deep-state conspiracy; it’s not far short of Pizzagate or QAnon territory. To take it seriously you have to believe in a vast international conspiracy involving thousands of scientists, not one of whom dares speak out.

Yet this paranoid fantasy has in effect become the official position of the G.O.P. Climate change deniers have pretty much given up on arguing about the evidence, although the old line “it’s a cold day, so global warming is a myth” still pops up now and then. Instead, it’s all about the supposed conspiracy.

What’s the evidence for this conspiracy? A lot of the argument rests on things like out-of-context quotes from stolen emails (sound familiar?), such as those sent among researchers at the University of East Anglia’s Climate Research Unit. Like the texts between two F.B.I. officials that supposedly prove the existence of a plot against Trump, “Climategate” actually showed nothing more than that the people involved were human. But to a determined conspiracy theorist, everything is evidence of nefarious activity.