President Donald Trump, who has reveled in his confrontational style with the news media, sparked fierce debate Sunday over whether he is inciting violence against journalists by posting a doctored video clip showing him bashing the head of a figure representing CNN.

Trump's latest provocation in his war with the media brought denunciations from Democrats, and some Republicans, who warned that the president's conduct could endanger reporters as he seeks to undermine public trust in reporting about his administration.

"Violence & violent imagery to bully the press must be rejected," House Minority Leader Nancy Pelosi, D-Calif., wrote in one of the many comments from elected officials posted on Twitter.

Presidential historians suggested that Trump's social media attacks are lowering the bar on what constitutes appropriate presidential conduct in fighting perceived media enemies. H.W. Brands, a historian at the University of Texas, said Republican President Richard Nixon also felt mistreated, but "Nixon didn't air his grievances as publicly as Trump does. We've never seen anything quite like the ongoing performance of President Trump."

Meanwhile, White House aides and supporters defended the president's Twitter post as a pointed but harmless barb at what he sees as a hostile press corps. Some said the reaction demonstrated the inflated self-regard of reporters and their inability to take a joke.

Trump, from his Bedminster golf resort in northern New Jersey, defended his use of social media, saying it befitted a "modern day" president.

The latest salvo from Trump came as questions about the political climate for journalists, and their safety, have swirled amid incidents in which politicians have assaulted reporters or had them arrested. During the campaign, some reporters assigned to cover Trump, including ones from CNN, were cursed and threatened by his supporters, who echoed him with chants of "fake news."

In a statement, the Committee to Protect Journalists said that targeting media outlets "creates a chilling effect and fosters an environment where further harassment or even physical attack is deemed acceptable."

The organization, which tallies deaths of journalists across the globe, added that the White House's "charged rhetoric online" makes reporting "more dangerous" and "emboldens autocratic leaders around the world."

Trump had been combative with the news media throughout his campaign and in the first months of his presidency. But his anger and frustration have mounted in recent weeks amid intensive coverage of an FBI investigation into his campaign's alleged contact with Russian operatives, who U.S. intelligence agencies determined meddled in the presidential election in hopes of aiding Trump.

White House aides have fretted that the president's focus on the investigation has distracted him from building political support for his policy agenda, including a legislative rollback of the Affordable Care Act that is now pending in the Senate. And some of his public statements have embroiled him more deeply in legal questions over his conduct in the probe.

At the same time, the president and his aides believe that his feud with the media, which has included limiting the number of on-camera briefings, has played well with his conservative base. Late Saturday, Trump used a portion of a speech at "Celebrate Freedom" event at the Kennedy Center, in honor of military veterans and religious groups, to taunt the press.

"The fake media is trying to silence us, but we will not let them. The people know the truth," Trump said. "The fake media tried to stop us from going to the White House, but I'm president and they're not."

He drew a standing ovation from the crowd, which waved miniature American flags. On Sunday afternoon, Trump posted a video clip of the moment on Twitter.

Aides defended his tweet of the WWE video on Saturday, arguing that Trump has a right to fight what they say is unfair coverage. They suggested that reporters were overreacting to a video first posted several days ago on the popular social media message board Reddit.

"No one would perceive that as a threat; I hope they don't," homeland security adviser Tom Bossert said on ABC's "This Week."

Bossert praised Trump's ability to "genuinely" communicate with the public, and he echoed a line of defense that other Trump surrogates have employed: that when Trump's policies are attacked in the media, he has a right to counterpunch.

"He's beaten up, in a way, on the cable platforms," Bossert said. "He has a right to respond."

The video clip was taken from a WWE appearance in 2007 during which Trump body-slammed WWE Chairman Vince McMahon as part of the "Battle of the Billionaires." Trump, a New York real estate developer and promoter, has had a long association with the WWE and was inducted into its Hall of Fame in 2013. At the ceremony, McMahon referred to Trump as "a Wrestlemania institution" and recalled this episode, which culminated with Trump participating in shaving McMahon's head in the ring.

Trump has appointed McMahon's wife, Linda, who donated $6 million to a pro-Trump super PAC, as the head of the federal Small Business Administration.

On Reddit, users on a pro-Trump message board where the wrestling video meme first appeared celebrated their achievement in getting the president to endorse their work. Some Trump supporters emphasized on social media that the violence in professional wrestling is simulated and that the president was making a symbolic point about "fake news" coverage of him.

But Trump's critics pointed to Rep. Greg Gianforte , R-Mont., who body-slammed Ben Jacobs, a reporter for the Guardian, in May - one day before a special election, which he won. Gianforte, who initially denied Jacobs' account, later apologized to him and was sentenced in court to 40 hours of community service and 20 hours of anger management classes.

Within seven hours, Trump's post of the wrestling video had been "liked" 317,000 times and "retweeted" 198,000 by Trump's 33 million Twitter followers - one of his most viral tweets in months. The president also posted the clip to his official White House account.

In recent days, Trump has leveled deeply personal attacks at morning show hosts from MSNBC who have criticized him. On Saturday, he called CNN "fake news" that produces "garbage journalism." The president and his aides have lambasted the network in the wake of a retracted story that linked a former Trump transition aide to a Russian bank executive. Three CNN employees resigned over the story, which the network said did not go through proper vetting.

In a statement Sunday, CNN called it "a sad day when the President of the United States encourages violence against reporters." The network cited Trump's "juvenile behavior far below the dignity of his office."

Floyd Abrams, the First Amendment lawyer who argued for the publication of the Pentagon Papers before the Supreme Court, described the president's tweet Sunday as "merely abhorrent," but fully protected by the constitution.

"I think it is foul. It is repulsive. But it is not illegal," Abrams said. "The president has First Amendment rights, too. While he may abuse them sometimes, it takes more than he has done so far to move into the area of illegality."

David Schulz, another free-speech lawyer, recalled Trump's suggestion during the campaign that "Second Amendment people" might be able to stop Democratic rival Hillary Clinton - a declaration some interpreted as an allusion to gun violence.

That was "a lot closer to the line than this childish screenplay," Schulz said.

Timothy Naftali, a presidential historian at New York University, cited the false "Pizzagate" conspiracy theory that last year prompted a North Carolina man to "self-investigate" social media claims that a child-sex ring was being run out of Comet Ping Pong, a restaurant in Northwest Washington, by Hillary Clinton.

The man fired a gun inside the restaurant; no one was physically hurt but the man was sentenced to four years in prison.

"No president has publicized his hatred for the media in the way Donald Trump has," Naftali said. "It's not a fake fear. People can be radicalized by things like this."

Wagner and Gregg reported from Washington. Karoun Demirjian in Washington contributed to this report.