For Richard Nixon, the "Saturday Night Massacre" was the beginning of the end.

The nation finally turned against the embattled president after he forced out −on Oct. 20, 1973 − the attorney general and his deputy who refused to get rid of the special prosecutor investigating him. A week later, for the first time, a plurality of Americans favored impeachment. And 10 months later, he resigned.

But Nixon didn't have Fox News in his corner.

President Donald Trump does. That might make all the difference if he were to fire Deputy Attorney General Rod Rosenstein or even special counsel Robert Mueller III. The pro-Trump media, led by Fox, would give cover, and huge swaths of Americans would be encouraged to believe that the action was not only justified but absolutely necessary.

You can see it coming.

Night after night − for many months − Trump's sycophant-in-chief, Sean Hannity, has been softening the ground. And his message is sinking in. In a recent Reuters/Ipsos poll, three of four Republicans said they believed the Justice Department and the FBI are actively working to undermine Trump.

"Hannity has been poisoning the well for Mueller's 'deeply corrupt' investigation and laying the groundwork to support the president if he seeks an authoritarian recourse," wrote Matthew Gertz, of the progressive watchdog group Media Matters for America. That was back in October.

Six months, five convictions and more than a dozen indictments later, that poison has done its job.

And the doses of propaganda keep coming.

"This man's track record is atrocious," Hannity ranted one evening last week about Mueller, calling his investigation "the biggest abuse-of-power scandal in the country's history." 

He spent part of his show trying to explain away a previous day's appalling graphic, depicting "the Mueller Crime Family," which had brought reasonable criticism from the reality-based press. Then he brought on former Trump aide and noted Islamophobe Sebastian Gorka, who readily tore into a former FBI director and the mainstream media: "James Comey is a liar, and CNN is a bunch of perverts."

The fulmination finds a ready audience: Fox News remains the most-watched cable news network and Hannity is its biggest star. (He has had, for many months, the top-rated cable show, though it has been edged out in recent weeks by MSNBC's left-leaning Rachel Maddow.)

That's not to say that Fox, which has been on air since 1996, is the most trusted of the three; a recent poll suggests otherwise. Even Fox insiders cringe, and sometimes quit. Just weeks ago, the conservative former Army lieutenant colonel Ralph Peters left his post as a Fox contributor, expressing disgust in a resignation letter that was leaked to BuzzFeed.

"Today, I feel that Fox News is assaulting our constitutional order and the rule of law, while fostering corrosive and unjustified paranoia among viewers," Peters wrote.

And some of Fox's own editorial employees have told CNN's Oliver Darcy that they are mortified by the Mueller coverage.

It's entirely possible, of course, that Trump won't take the drastic action of firing either Rosenstein or Mueller, though his spokeswoman asserted just days ago that he believes he has every right to do so and his former Svengali, Steve Bannon, is reportedly pushing in that direction.

Even with the approval of Trump's base, the move would be politically risky and might not accomplish much anyway: The investigation would go on.

But if he does, there will be a cheering section. Though Fox has the biggest megaphone, it's far from alone in its campaign to discredit Mueller.  Breitbart News, for example, touted a story last week at the top of its home page that opined, "Mueller is now much more widely seen, not as a man investigating a legitimate crime, but as a zealous prosecutor investigating a man in the hopes of finding a crime that will overturn a presidential election." 

Last November, a widely circulated Vox piece posited an alarming scenario in which Mueller's investigation would find serious wrongdoing by Trump but result in no consequences amid America's tribal politics.

"Say the entire right-wing media machine kicks to life and dismisses the whole thing as a scam and conservatives believe them," it suggested. "The conservative base remains committed to Trump, politicians remain scared to cross the base, and U.S. politics remains stuck in partisan paralysis, unable to act on what Mueller discovers."

The same dynamic might hold if Trump were to fire Rosenstein or even Mueller.

Millions of Americas might take to the streets, but just as many would be nodding their approval from their living rooms, with Fox and its ratings star Hannity leading the applause.

Margaret Sullivan is The Washington Post's media columnist.