WASHINGTON — Margaret Thatcher famously declared that “we must try to find ways to starve the terrorist and the hijacker of the oxygen of publicity on which they depend.”

In a speech 32 years ago, Mrs. Thatcher, the British prime minister facing a threat from the Irish Republican Army, said she was not calling for censorship but proposing that “a voluntary code of conduct” for journalists might keep them from aiding “the terrorists’ morale or their cause.”

It was a high-profile statement of a familiar point, one made repeatedly in the decades since: that the news media plays a crucial role in amplifying the impact of terrorist violence and giving it exactly the political import the terrorists crave.

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So for some experts who study terrorism, President Trump’s assertion this week that the news media has actually been ignoring and covering up terrorist attacks came as a surprise.

“It’s totally astonishing,” said Martha Crenshaw, a Stanford scholar who has written on terrorism since the 1970s. “It has no basis in fact whatsoever. The criticism has always gone the other way.”

Other experts said Mr. Trump’s claim had less to do with the facts about terrorism coverage than with the new administration’s political goals, notably defending his executive order that temporarily bans refugees and visitors from some Muslim countries. In the face of the onslaught of legal challenges and outspoken opposition to the order, they said, the president has an interest in persuading Americans that the terrorist threat from abroad is worse than the news media has revealed.

Years of books and articles critiquing the “symbiosis” of terrorism and media coverage have pointed out that terrorists usually seek to promote a political or ideological cause and use spectacular violence with the specific goal of attracting media attention. News executives, while sometimes expressing mixed feelings about giving terrorists what they seek, have generally felt obligated to give such attacks ample coverage.

“It’s incredible to say that the media does not give enough attention to terrorism,” said David C. Rapoport, a retired U.C.L.A. political science professor considered a founder of terrorism studies. He said modern global terrorism arose in the 1880s in Russia in parallel with, and partly owing to, the rise of mass daily newspapers.

In the United States since the Sept. 11 attacks of 2001, even failed terrorist plots often have drawn saturation coverage — think of the fizzled so-called underwear bomb on a Detroit-bound airliner on Christmas Day in 2009 or the S.U.V. jury-rigged to blow up that produced only smoke in Times Square on a May night in 2010. Though no target was harmed, both attempts drew mountains of coverage, much of it focused on how terrorists went undetected.

But in an appearance Monday at MacDill Air Force Base in Tampa, Fla., Mr. Trump reviewed the horrors of more recent attacks, including those inspired or directed by the Islamic State, and pronounced the coverage inadequate.

“Radical Islamic terrorists are determined to strike our homeland as they did on 9/11, as they did from Boston to Orlando to San Bernardino,” he said at the headquarters of Central Command, which carries out military operations in the Middle East. “All over Europe it’s happening. It’s gotten to a point where it’s not even being reported and, in many cases, the very, very dishonest press doesn’t want to report it. They have their reasons, and you understand that.”

The president did not explain the reasons he believed journalists might have for not reporting Islamist terrorism. But in response to a wave of skeptical comment, the White House on Monday night released a list of 78 attacks around the world since September 2014.

“Most have not received the media attention they deserved,” the accompanying statement said.

Sean Spicer, the White House press secretary, stood by the point on Tuesday, though adjusting the language. “It’s becoming too often that we’re seeing these attacks not get the spectacular attention that they deserve,” he said. “And I think it undermines the understanding of the threat that we face around this country.”

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It was a subjective judgment; only a dozen of the 78 listed attacks occurred in the United States, and most resulted in few or no deaths, reducing their prominence in American media reports. The list omitted terrorist attacks by non-Muslims, including white supremacists like Dylann S. Roof, who killed nine African-Americans at a Charleston, S.C., church in 2015.

But news databases show virtually all 78 attacks got some coverage, and the big attacks in Paris, Brussels, Boston, San Bernardino and Orlando played out for days or weeks on cable television and news sites.

Peter D. Feaver, a Duke political scientist who studies public opinion on national security issues, said he saw no basis for the White House claims. “I don’t think there’s evidence of the press underreporting terrorism,” he said. “The corporate incentives run the other way.”

But Mr. Feaver, who served in the George W. Bush White House but publicly opposed Mr. Trump during the presidential campaign, said the president’s remarks, if not literally true, nonetheless play out in a larger, partisan debate about terrorism.

Democrats sometimes accused the Bush administration of exaggerating the terrorist threat. Republicans often charged President Barack Obama of minimizing the danger and embellishing his own successes against Al Qaeda. By suggesting that the mainstream media is hiding the truth about the menace from “radical Islamic terrorists,” Mr. Trump may rally his base behind the executive order and other measures still to come.

Mr. Spicer suggested as much, saying the executive order and the president’s remarks in Tampa have the same motive: “because he cares about making sure that we don’t have attacks in this country, that we’re protected.” Mr. Trump wants Americans, he said, to “understand the unwavering commitment that the president has and the actions that he will take to keep the country safe.”

Preventing terrorist attacks is, of course, a goal that is pretty much universally shared. But Mr. Trump’s loose relationship with facts, and his eagerness to fault journalists and judges, make some think he has a less lofty goal as well: to find scapegoats for terrorist attacks that sooner or later are certain to happen.

“Pre-emptive blame,” said Ms. Crenshaw, the Stanford terrorism researcher. “Nothing’s happened. But if something does happen, he can blame the judiciary and the news media.”