The revelation that Donald Trump’s son, son-in-law and campaign manager met with a Kremlin-connected Russian lawyer promising information that would “incriminate” Hillary Clinton was a true bombshell in an era when we have become almost inured to them. Here was proof that members of Mr. Trump’s presidential campaign had, at the very least, been eager to collude with Russia to influence the 2016 election.

No one could gainsay the facts: Mr. Trump’s own son published them on Twitter.

As recently as five or 10 years ago, every major news outlet would have treated this set of facts as front-page news and a dire threat to Mr. Trump’s presidency. The conservative press and Republican voters might disagree on certain particulars or points of emphasis. But their view of reality — of what happened and its significance — would have largely comported with that of the mainstream. You’d have had to travel to the political fringe of right-wing talk radio, the Drudge Report and dissident publications like Breitbart News to find an alternative viewpoint that rejected this basic story line.

Not anymore. Look to the right now and you’re apt to find an alternative reality in which the same set of facts is rearranged to compose an entirely different narrative. On Fox News, host Lou Dobbs offered a representative example on Thursday night, when he described the Donald Trump Jr. email story, with wild-eyed fervor, like this: “This is about a full-on assault by the left, the Democratic Party, to absolutely carry out a coup d’état against President Trump aided by the left-wing media.”

Mr. Dobbs isn’t some wacky outlier, but rather an example of how over the last several years the conservative underworld has swallowed up and subsumed more established right-leaning outlets such as Fox News. The Breitbart mind-set — pugnacious, besieged, paranoid and determined to impose its own framework on current events regardless of facts — has moved from the right-wing fringe to the center of Republican politics.