By Cokie Roberts and Steven V. Roberts

Many of Donald Trump’s tweets are impulsive and repulsive, inaccurate and incendiary. But one of his recent blasts on social media was correct: “My use of social media is not Presidential — it’s MODERN DAY PRESIDENTIAL.”

Trump has shrewdly and successfully used social media to spread his message directly to his supporters without the messy and annoying scrutiny of mainstream journalists. In effect, he’s created the TBN, the Trump Broadcasting Network. And with more than 30 million followers on Twitter alone — who can then retweet his missives to their own connections — his reach is enormous.

Trump’s probably right when he says that without social media, he would not be president. “The FAKE & FRAUDULENT NEWS MEDIA is working hard to convince Republicans and others I should not use social media,” he tweeted, “but remember, I won the 2016 election with interviews, speeches and social media. I had to beat #FakeNews, and did. We will continue to WIN!”

But the larger and more critical question is what he actually says on social media now that he’s president. How does he use this powerful platform to convey his policies and values?

To his core followers, he’s still a hero. But to many Americans, including a growing number of Republicans, he’s not winning on social media. He’s losing. Instead of elevating public discourse, he’s lowering it; instead of dignifying his office, he’s demeaning it.

In a recent NPR/Marist poll, 7 out of 10 Americans, with little partisan difference, agree “the level of civility in Washington has gotten worse since President Trump was elected, while just 6 percent say the overall tone has improved.” And Trump’s vitriolic diatribes on Twitter contribute heavily to that climate of contentiousness.

In a Politico poll, 69 percent said Trump tweets too much. Fifty-nine percent called his Twitter habit a “bad thing” and only 23 percent called it a “good thing.” Even Sen. Mitch McConnell, the Republican leader, concedes that he’s “not a great fan” of Trump’s tweets.

The president’s repeated outbursts dominate news coverage and drain energy and attention away from his own legislative agenda.

The news media has long been a favorite target of Trump’s social media machine, and lately his obsession has gotten worse. He’s pursued an inane vendetta against morning talk show hosts Joe Scarborough (“Psycho Joe”) and Mika Brzezinski (“low I.Q. Crazy Mika”). And he’s repeatedly labeled CNN “fake news” and “garbage journalism.”

Trump reached a new low, even for him, when he posted an old video of himself, made to promote pro wrestling, pummeling an opponent to the ground. The foe’s head, however, is replaced with the distinctive CNN logo.

In the current climate, where a deranged shooter feels free to attack Republican congressmen just because of their politics, journalists rightly fear for their safety. But the president’s real goal is not to endanger journalists’ security — it’s to undermine their credibility.

His tweets might seem unhinged, but there’s a careful strategy behind them.

He’s trying to convince voters that they should not believe his critics. In Trump’s Twitter World, there are no independent provable facts, only “fake news.” The president alone knows The Truth. Anyone who contradicts him is “psycho” and “crazy” and speaking “garbage.”

This is profoundly dangerous. The president is deliberately trying to cripple an essential element of democracy, the ability of a free press to hold the leaders of the country accountable.

Other presidents have despised the press — Richard Nixon comes to mind — but Nixon didn’t have Twitter.

“Nixon didn’t air his grievances as publicly as Trump does,” historian H.W. Brands said in the Washington Post. “We’ve never seen anything like the ongoing performance of President Trump.”

No, we haven’t, and he’s having an effect, at least on his most partisan supporters. A recent Pew poll found that 70 percent of Americans feel the media “keeps political leaders from doing things that shouldn’t be done.” But while 89 percent of Democrats share that view, only 42 percent of Republicans embrace the media’s watchdog role.

Between the two of us, we’ve spent almost 100 years as professional journalists, devoted to the principles that Trump denigrates every day. We believe deeply that journalists must protect the public by preventing their leaders from “doing things that shouldn’t be done.”

But we also believe that journalists must perform that role accurately and ethically. No cheap shots or flimsy stories. Resist the pressure to be first and wrong. The media can be fair to the president and still be fearless.

Steve and Cokie Roberts can be contacted by email at stevecokie@gmail.com.