Call it the Fox News Caucus.

Rather than having their staffers compile questions about Russian interference in the 2016 presidential election, the GOP members of the judiciary and intelligence committees took their cues and, at times, their very words from Fox News figures like Sean Hannity as they questioned former special counsel Robert Mueller last month about the results of his probe.

The result was a stew of references to bit players like the intelligence firm Fusion GPS and its founder, Glenn Simpson, that were largely opaque to those unfamiliar with the network’s efforts to portray President Donald Trump as the victim of a baroque partisan witch hunt. And a few days later, Texas Rep. John Ratcliffe, one of the Republican congressmen pushing the conspiracy theory, had been named by Trump as the next director of national intelligence. (Ratcliffe withdrew from consideration following media reports that he had inflated his terrorism bona fides and was “disengaged” from the intelligence committee's work.)

The episode -- already fading from memory given the breakneck pace of the news cycle -- serves as a startling case study of how a cable news network essentially runs a large portion of the U.S. government.

The president himself is famously Fox’s biggest fan. But the Mueller testimony was a vivid illustration for a national audience of just how intently congressional Republicans have also fallen under the network’s sway. At best, their focus on Fox's coverage renders these GOP members unmoored from the issues of the day, leaving them unable to participate in crucial debates about past and future Russian attacks on our elections. At worst, their obsession with their propagandists’ ephemera sidetracks these debates and drags the rest of the country into their fever swamps.

While Fox has influenced GOP politics since the network’s inception, Trump’s unprecedented relationship with the network has drastically increased its power. The president is a rapacious consumer of Fox programming, which he uses as a source of political cues and policy ideas. In response to Fox segments, Trump has triggered a weeks-long partial shutdown of the federal government; set off international incidents from North Korea to South Africa to Sweden; and incited a feud with racist tweets about progressive Democratic congresswomen.

Republican politicians have taken an important lesson from this feedback loop: They can use Fox to gain power in their party.

Former House Speaker Paul Ryan (R-WI) reportedly struggled because he did not share the president’s obsession with the network’s insipid morning show, Fox & Friends. By contrast, Ryan’s replacement, Rep. Kevin McCarthy (R-CA), auditioned for the gig by fawning over the president on the program, and he is a regular guest on Trump’s favorite hours of Fox. Republican members of Congress talk up their ideas for bills on the network’s shows in hopes of capturing the president’s attention. Sometimes, they even privately take the temperature of Trump’s favorite Fox hosts prior to going public with their proposals.

But Mueller’s probe provides the clearest evidence of just how deeply Fox has shaped the thinking of congressional Republicans.