President Trump and his supporters have seized on a single line in a CNN article to question the credibility of the story and of the network. Why, they ask, was a key source for the article described as not commenting when he later admitted that he very much had?

The question and the criticism open up a broad — and arguably unflattering — vista on the way journalism sometimes works.

CNN has stood by the story, published on July 26 under the byline of three writers, including legendary Watergate reporter Carl Bernstein. The article reported that former presidential lawyer Michael Cohen was prepared to tell special counsel Robert S. Mueller III that he knew that Trump was aware in advance, and had approved, a fateful meeting with Russian operatives at Trump Tower during the 2016 presidential campaign.

Trump has repeatedly denied any prior knowledge of the meeting, in which top campaign officials met with the Russians with the expectation of receiving unflattering information about Hillary Clinton.

The story reported prominently that one of Cohen’s attorneys, Lanny Davis, had declined to comment on the matter.

In fact, CNN was well aware that Davis had commented plenty. The reason: He was one of CNN’s key sources, albeit a “background” source, one who divulges information with the promise of anonymity. Davis himself later acknowledged he was a source, outing himself in an interview . . . on CNN ; Davis subsequently backed off the claims he made in the story, but CNN is standing by it, saying other sources have corroborated its reporting.

So how to square the CNN article’s original statement that Davis “declined” to comment when he clearly was among those speaking to the reporters?

Strictly speaking, Davis did decline to “comment” — if comment means a direct, on-the-record statement. Davis is not quoted by name in CNN’s article.

Further, people at CNN defend the Cohen-Davis piece by asserting that there’s no contradiction between a reporter speaking to a source on a background basis and then saying that same person declined to comment. Although readers and viewers often aren’t aware of it, “it’s done all the time in Washington,” said one person at CNN, who — yes — declined to be identified or to make an “on-the-record” comment.

But critics say the practice is murky at best and ethically dubious at worst. Reporting that someone “declined to comment” when he or she actually had could mislead readers into believing an individual had no role in shaping a story.

“If CNN did tell its readers and viewers that Davis did not comment when he was indeed one of their confidential sources, that breaks a bond of trust with the public,” said Kathleen Culver, director of the Center for Journalism Ethics at the University of Wisconsin. “It’s deceptive and wrong. And if it is the case, CNN needs to be as transparent as possible immediately and develop practices to ensure this never happens again.”

It’s not clear how widespread this practice is among reporters or how long it has been used. Mainstream news organizations officially frown on saying someone didn’t comment when they actually spoke on background or off the record (meaning not for attribution or publication in any way). But this guideline isn’t always enforced.

To avoid running afoul of this general rule, reporters sometimes avoid mentioning whether they asked a source for comment. Or they’ll use qualifying language, such as the phrase “declined to comment on the record.” This formulation is intended to signal that a source didn’t want to be directly quoted while leaving open the possibility that the individual supplied background information for the story.

But this kind of workaround has its own defects. It could suggest to savvy readers that the source played some role in the story — the very thing anonymous sources are eager to avoid.

The alternative could be worse. “Double dipping” — suggesting a source didn’t comment when he actually did — “really is deceptive,” said W. Joseph Campbell, a media historian and communication professor at American University. “I can see the motive for a reporter to [say a source didn’t comment]. They want to protect a source and throw everyone off the scent. But I still think it’s unethical, improper and misleading to readers.”

Ironically, Trump, who has repeatedly blasted the CNN article on Twitter, has been an anonymous source and an eager manipulator of stories about himself for decades. He has even taken on false personas — once posing as fictitious public-relations executives named John Barron and John Miller — to plant favorable stories about himself.

As president, Trump has occasionally phoned reporters and fed them information that he insists be attributed to “a senior White House official,” according to author Ronald Kessler. Implicit in these stories is that the president wasn’t directly involved in them, when he actually was.

But Trump’s practice doesn’t let media outlets off the hook, said veteran reporter and editor Glenn Greenwald, who wrote a scathing critique of CNN’s handling of Davis-Cohen story on his website, the Intercept .

“News organizations never have the right to lie to their readers, and when they deliberately do, it’s scandalous,” said Greenwald in an interview. Had readers known of Davis’s role, he said, “we could have assessed the story with much greater skepticism.”

Cohen and Davis, he pointed out, had a direct, vested interest in making claims about Trump’s foreknowledge of the Trump Tower meeting. Davis, for example, might have been pushing the story to help his client, who is facing a long prison sentence, pressure Trump into granting him a presidential pardon, he said.

“But by explicitly lying that Davis refused to comment, it deliberately cast the appearance that this wasn’t something purposely put out by [Davis] but had a more credible provenance — maybe Mueller’s office, maybe [a member of] Congress,” Greenwald said. “It vested the story with far more significance and credibility than it deserved.”

CNN, he said, “purposely broadcast a clear statement that was a lie. This cannot possibly be justified if journalists want to also have the role to demand truth from other institutions. . . . Who believes someone who knowingly lies to you?”