President Richard Nixon tells journalists at a White House news conference in March 1973 that he will not allow his legal counsel, John Dean, to testify on Capitol Hill in the Watergate investigation. (CHARLES TASNADI/Associated Press)

Mark Feldstein, Eaton chair of broadcast journalism at the University of Maryland, is the author of “Poisoning the Press: Richard Nixon, Jack Anderson, and the Rise of Washington’s Scandal Culture.”

Donald Trump’s recent declaration of war against The Post is reminiscent of another angry thin-skinned Republican who launched a nasty crusade against the media: Richard Nixon.

Trump’s Nixonian echo is hard to miss. Both men relished vendettas against the media and political establishments: Nixon viewed the press as “the enemy”; Trump calls it “scum.” And both professed to champion America’s “silent majority,” invoking an angry faux-populism to blame racial minorities for legitimate economic grievances.

Like Trump, Nixon’s battles with the press began long before his march to the White House. He, too, obsessively sought to manipulate the news coverage he desperately craved and wasn’t afraid to use intimidation if he thought it would help. Nixon’s conduct in office presents a chilling example of what a President Trump could do.

Nixon’s sense of grievance was genuine, going back to his narrow defeat in 1960 by John F. Kennedy and his self-pitying vow two years later that “you won’t have Nixon to kick around anymore.”

To his surprise, Nixon’s attack on the press tapped into growing right-wing fury at media elites. It proved to be not his valedictory but the opening salvo of his successful comeback in 1968.

Other conservative politicians of the era — George Wallace, Barry Goldwater — similarly discovered that they could win votes by attacking the press.

The tactic would become known as “working the refs,” and it would become an effective political staple ever after — including Sarah Palin’s denunciation of the “lame-stream media” and Trump’s ban of “dishonest” reporters from campaign rallies.

Nixon understood this better than anyone. “If we treat the press with a little more contempt,” he told his staff, “we’ll probably get better treatment.”

Indeed, Nixon did more to try to undermine the news media as an institution than any president in history. Just a few months after his election, he dispatched Vice President Spiro Agnew to launch a public assault on the “small and unelected elite” of journalists who held a “concentration of power over American public opinion unknown in history.” Nixon publicly said that he hadn’t heard Agnew’s speech. In fact, he had privately approved it word-for-word ahead of time, chortling that it “really flicks the scab off.

In addition, Nixon invited top broadcast executives to the White House and told them that “your reporters just can’t stand the fact that I am in this office.” Press Secretary Ronald Ziegler declared that all of the TV networks were “anti-Nixon” and would “pay for that, sooner or later, one way or another.” Another top adviser, Charles Colson, told the head of CBS News that Nixon’s administration would “bring you to your knees” and “break your network.”

The president acted on his threats. Six weeks after Agnew’s public attacks, a business partner of Nixon’s best friend filed paperwork with the government to challenge The Post’s ownership of its lucrative Florida TV station. The Post should be given “damnable, damnable problems” getting its FCC licenses renewed, Nixon told his staff. “There ain’t going to be no forgetting and there’ll be goddamn little forgiving.” The president also instructed aides to “screw” The Post by inciting shareholders to “go after” publisher Katharine Graham by targeting The Post’s real estate investments.

Furthermore, Nixon’s otherwise pro-business Justice Department filed anti-trust charges against the three television networks, accusing them of monopolistic practices. Federal prosecutors drafted legislation to make it a felony for journalists to receive unauthorized leaks. More ominously, Nixon approved illegal wiretaps on reporters who criticized the administration.

Would a President Trump behave likewise? He has already suggested that he would like to change libel laws so that when news organizations publish a “hit piece” that is “purposely negative and horrible and false . . . we’re going to . . . sue you like you’ve never been sued before.”

Still, Trump’s animosity toward the press — like so much of his act — may be more contrived than real. After all, he is in many respects a media creation, built up by nearly $2 billion in free publicity that helped him shock the political establishment by vanquishing 16 GOP opponents in less than a year.

In part, Trump can thank Fox News — and Nixon. Despite its skirmishes with Trump, Fox News spent years helping the casino magnate transition to politics by giving him a national platform to opine on public affairs. And it was Nixon who, decades earlier, suggested creating a TV network like Fox News to provide conservative news programming. It would take another quarter-century before Nixon’s former campaign aide, Roger Ailes, could make good on his boss’s dream.

The parallels between Nixon and Trump shouldn’t be overstated. Nixon almost always presented a respectable facade, while billionaire Trump, unburdened by bourgeois niceties, is accustomed to getting his way without annoying distractions like political compromise. Whether Trump would be more dangerous than Nixon, or less, is as impossible to know as whether Trump is genuinely committed to his outrageous political stands; perhaps his views are simply cynical and expedient manipulations, the extreme opening bids of a professional negotiator whose only real goal is producing a workable deal.

But if history has taught us anything, it is that we ignore would-be authoritarians at our peril. When it comes to the media, Trump is Nixon’s echo — and, perhaps, Nixon’s revenge.