Several journalists surely knew who Stormy Daniels was in 2016, and it probably wasn't because they had seen her in one of the many porn films she had made.

The adult-film actress was on the radar of a number of mainstream news outlets in the waning days of the presidential campaign. Reporters from ABC, Fox News, the Daily Beast and Slate.com were pursuing a potentially explosive story: that Daniels had allegedly had an affair with Donald Trump in 2006, only months after Trump's wife, Melania, had given birth to their son, Barron.

Yet no one went with the story.

Given the context and potential importance of Daniels' story — on the heels of multiple sexual assault allegations against Trump and the controversy over his vulgar remarks on the "Access Hollywood" video — the question is, why? Why wasn't the story reported at the time, when it might have intensified questions surrounding Trump's character just before voters went to the polls?

Journalists say they held back because they couldn't independently corroborate key elements of Daniels' account, including in one instance from Daniels herself. The story, in other words, failed to rise to journalistic standards, never mind that it involved a man who regularly attacks the news media for lacking standards.

The story behind the story began to spill out only in the past week, touched off by a Wall Street Journal report about Michael Cohen, a lawyer for the Trump Organization. The Journal reported that Cohen arranged a $130,000 payment to Daniels a month before the election in 2016 in exchange for her silence about an alleged sexual relationship with Trump. Daniels, Cohen and the White House have denied any such relationship; she also denied in a statement issued by Cohen that she was paid "hush money" by Trump.

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The most advanced reporting on the story in 2016 appears to have been done by Jacob Weisberg, the editor of the Slate Group. After receiving a tip about Daniels, Weisberg spoke with Daniels and exchanged text messages with her multiple times starting in the summer of 2016 — all of it on the record, meaning there were no restrictions on its publication. He also spoke to three of her friends, all of whom "confirmed the outlines of her story," according to Weisberg's account, published Tuesday by Slate.

In addition, Weisberg said he received a two-page document from Daniels that appears to be a nondisclosure agreement that binds her to silence about the terms of a settlement. The document identifies the other party only as "David Dennison a.k.a. (blank)."

But that was the end of that. Daniels stopped responding to Weisberg a week before the election, leaving him in the dark about crucial details. While he was aware of the alleged affair, Weisberg said he lacked independent corroboration of the confidentiality settlement. He calls that the most important part of the story. (The Smoking Gun website had already published details of the alleged affair in mid-October, to little public notice or reaction.)

"In sum, we just didn't have the story in a form that we could use it," Weisberg said in an interview.

He added: "I don't think we were too cautious (in not publishing at the time). We just didn't have it nailed down. I regret that we couldn't publish it, but not that we didn't publish it under the circumstances."

The Daily Beast's executive editor, Noah Shachtman, said his publication decided not to go with a story despite having three sources confirming the affair, including one on the record, Daniels' friend Alana Evans. (Evans recounted her story on the "Today" show on Tuesday.) Daniels herself was ready to confirm it as well, he said, but she backed out of an interview on Nov. 3, apparently after signing the nondisclosure agreement. That defection was critical; Shachtman said the Daily Beast would have published if Daniels had confirmed what other sources were already claiming.

"Without that first-person confirmation, we didn't feel comfortable running the story, especially with just a few days to go before the election," he said. The website's reporters periodically checked back in with Daniels' camp but were told she wasn't talking. "Now we know why," he said, referring to the nondisclosure agreement.

ABC News and Fox News, both of which also pursued the story but didn't report it, declined to comment.

Of the two, Fox appears to have come closest; one of its reporters, Diana Falzone, reportedly filed an online story in October 2016 about an alleged sexual relationship between Trump and Daniels, according to CNN.com. The story was killed, though it's not entirely clear why. In a statement to CNN, Fox News digital editor Noah Kotch said, "In doing our due diligence, we were unable to verify all of the facts and publish a story."

Both the earliest and latest arrival to the story may be InTouch, the celebrity magazine. Despite Daniels' denials of an affair, the publication on Wednesday unearthed what it said was an interview with her in which she described a year-long sexual relationship with Trump — an interview the magazine conducted with Daniels in 2011 but never published.

Why did it take more than six years to print Daniels' account?

"I think that's everyone's question right now," said James Heidenry, InTouch's editorial director, in an interview. "I've only been here since November. I can't speak to decisions that were made before then."

Heidenry said the interview with Daniels, conducted by a former staffer, "had fallen off the radar" for the magazine's current staff and only "rang a bell" after Daniels landed back in the news last week. InTouch has not published the recording or made it public.

Daniels — who wasn't bound by a nondisclosure agreement at the time — spoke freely and at length about Trump to InTouch. Daniels and her then-husband, who corroborated his wife's account, both took polygraph tests supervised by the magazine and passed, Heidenry said.

Although voters were left in the dark about Trump's alleged relationship with Daniels before the election, news organizations' reluctance to publish the story suggests a high level of professionalism, said Tom Rosenstiel, executive director of the American Press Institute.

"It is not clear whether any news organization had the hush-money story (or the affair itself) in a verifiable form prior to the election," he said. "In journalism, you shouldn't publish what you believe to be true. You should only publish what you can prove."

Paul Farhi is the Washington Post's media reporter.