The extraordinary legal battle between the president of the United States and a former adult-film star has been building for seven years.

The standoff is rapidly escalating, as the porn actress, Stephanie Clifford, seeks to go public with details of her claims of an extramarital affair, and President Donald Trump and his attorneys fight to stop her.

A turning point came during a February phone call, after Michael Cohen, Mr. Trump’s personal lawyer, acknowledged publicly he paid Ms. Clifford $130,000 but didn’t say why.

In the call, Ms. Clifford’s lawyer told Mr. Cohen the actress believed his comments breached a nondisclosure pact they had signed in October 2016—and that she was now free to discuss the alleged affair.

“I didn’t f—ing breach it!” Mr. Cohen yelled, people familiar with the call said. Mr. Cohen warned her lawyer that if Ms. Clifford were to talk, he would seek to enforce the agreement.

It isn’t known whether Mr. Trump was aware of the agreement. But the Federal Election Commission is reviewing complaints by interest groups that the agreement violated campaign-finance law because of its timing, two weeks before the 2016 election.


The allegations pivot on whether the payment was made to influence the election to Mr. Trump’s benefit, said Thomas Frampton, a lecturer at Harvard Law School.

“It may be one of the least scintillating issues that Ms. Clifford could speak about, but from the perspective of Cohen’s and the president’s legal liability, it could be the most dangerous,” he said.

In a court filing Friday, Mr. Trump’s lawyers said they intend to pursue damages against Ms. Clifford—better known by her professional name, Stormy Daniels—for alleged violations of the contract, which they said could surpass $20 million. White House representatives and Mr. Cohen have denied any sexual encounter between Ms. Clifford and Mr. Trump, who hasn’t addressed the matter publicly.

The 39-year-old Ms. Clifford, who now mostly directs adult films and performs at strip clubs, has sued Mr. Trump, 71, seeking to extricate herself from the deal. She has taped an interview with “60 Minutes” expected to air this Sunday.

Donald Trump with Stephanie Clifford in a 2006 photo.

Ms. Clifford considered selling her story as early as April 2011, when she contacted her friend Greg Deuschle, a retired adult-film star known as Randy Spears.


At his urging, his ex-wife, Gina Rodriguez, a former pornographic actress-turned entertainment manager, called Ms. Clifford and offered to help.

Ms. Rodriguez sent an email to a reporter for Life & Style magazine, owned by Bauer Publishing, with the subject line, “Donald Trump Cheating Story.”

“I wanted to see if you were interested in a very bigh [sic] cheating story with Donald Trump and a Porn Star,” Ms. Rodriguez wrote, according to a copy of the email reviewed by The Wall Street Journal. “He was with her several times right after his current wife had there [sic] baby.”

Ms. Clifford agreed to Bauer’s $15,000 offer. Reporter Jordi Lippe-McGraw said she interviewed Ms. Clifford and recorded her discussing alleged encounters with Mr. Trump, starting with dinner and sex at his hotel room after they met at a celebrity golf tournament in Lake Tahoe in 2006, according to a transcript published by Bauer.


Lie-detector tests supported the accounts of Ms. Clifford, her ex-husband Michael Mosny and Mr. Deuschle, according to reports reviewed by the Journal.

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Former adult-film actress-turned manager Gina Rodriguez in 2011. Photo: WireImage/Getty Images

After the magazine called Mr. Trump’s representatives for comment, Mr. Cohen threatened to sue, say people familiar with the matter. Mr. Cohen, 51, didn’t respond to requests for comment.

He also called Ms. Clifford’s manager, Ms. Rodriguez, said Mr. Deuschle, who answered the phone.

“He said, ‘You tell Gina if she ever wants to work in this business again then she needs to call me immediately,’ ” Mr. Deuschle recalled.


Ms. Rodriguez instead called Keith Davidson, a Los Angeles lawyer with a history of representing people who had come into possession of compromising information about celebrities.

Mr. Deuschle said Mr. Davidson advised Ms. Rodriguez to back off the story, because Ms. Clifford lacked proof, other than the names of Mr. Trump’s bodyguard and one of his assistants.

In late May 2011, Life & Style informed Ms. Clifford’s camp it wasn’t publishing her story, according to an email reviewed by the Journal.

Ms. Clifford’s current lawyer, Michael Avenatti, said Friday in an interview on MSNBC that Ms. Clifford had been threatened with physical harm if she spoke publicly about interactions with Mr. Trump.

The White House didn’t respond to requests for comment. Mr. Cohen said in an interview with Vanity Fair published Monday he didn’t threaten Ms. Clifford. When asked if anyone else had, he said, “I can only speak for myself.”

Mr. Avenatti declined to comment in detail about Ms. Clifford’s earlier attempt to sell her story.

“Unfortunately, and despite the prior WSJ reporting which was credible, this story is far more fiction than fact. Too many inaccuracies to count,” he said in a written statement.

The story returned in October 2011, when a gossip website called “The Dirty” alleged that Ms. Clifford “had sex with Donald after one of his golfing events.” Ms. Rodriguez leaked the information to the site’s author, Nik Richie, he later revealed on his blog.

The post prompted Life & Style to publish a two-page spread about Mr. Trump’s alleged affairs with Ms. Clifford and other women—although it didn’t include the interview with Ms. Clifford.

Five years later, Mr. Trump’s rise from reality-television star to Republican presidential nominee presented Ms. Clifford with a more lucrative opportunity.

Mr. Cohen learned Ms. Clifford was again in discussions with news media and contacted Mr. Davidson in September 2016, a person familiar with the matter said.

Michael Cohen, President Donald Trump's personal attorney, after a private meeting with the Senate Intelligence Committee. Photo: Pablo Martinez Monsivais/Associated Press

Mr. Cohen told Vanity Fair that Ms. Clifford’s lawyer proposed the $130,000 figure. ​“He said that she needed the money,” Mr. Cohen said.

Ms. Clifford signed the contract on Oct. 28, 2016. Less than two weeks later, Mr. Trump won the election.

Several experts in campaign-finance law said the timing raises red flags. Whether the payment to Ms. Clifford amounted to a campaign contribution depends on whether it was coordinated with Mr. Trump or his campaign and whether Mr. Cohen would have paid Ms. Clifford irrespective of the election, they said.

Mr. Cohen’s willingness to negotiate in 2016 could amount to powerful evidence the payment was made “because Mr. Trump was Candidate Trump,” said Jessica Levinson, a law professor at Loyola Marymount University in Los Angeles.

In his Vanity Fair interview, Mr. Cohen said he made the payment out of friendship to Mr. Trump. “If she would have come to me a month before, or three months before, I would have done the same thing,” he was quoted as saying.

In January 2018, the Journal began asking about the nondisclosure agreement. Mr. Cohen requested Ms. Clifford and her attorney draft a denial, people familiar with the matter said.

Mr. Cohen emailed the Journal a statement signed by “Stormy Daniels,” denying that she had a “sexual and/or romantic affair” with Mr. Trump or received payment from him.

The Journal article revealing the $130,000 agreement ran on Jan. 12, 2018.

Five days later, Bauer dusted off the 2011 interview with Ms. Clifford and published it in its larger magazine, “In Touch Weekly.”

Ms. Clifford took advantage of the attention with media appearances. On the day of a Jan. 30 appearance on “Jimmy Kimmel Live!,” Mr. Davidson informed her Mr. Cohen wanted another statement of denial, people familiar with the matter said. Ms. Clifford was eager to appear on the show and complied, these people said.

She also got word that pornography publisher Larry Flynt was offering to pay her potential legal expenses if she told her story on air. Ms. Clifford, wary of the offer, maintained her silence as Mr. Kimmel pressed her for details. A spokesman for Mr. Flynt confirmed the outreach, but said “nothing came of it.”

The turning point for Ms. Clifford—when she began to seriously consider speaking out—was a statement Mr. Cohen provided to news media on Feb. 13 acknowledging the deal with Ms. Clifford, people familiar with the matter said.

“Just because something isn’t true doesn’t mean that it can’t cause you harm or damage,” Mr. Cohen said.

Ms. Clifford viewed his comment as Mr. Cohen calling her a liar, and she questioned why Mr. Cohen could speak freely while she had to remain silent, according to people familiar with the matter.

In the call soon after, Mr. Davidson told Mr. Cohen that Ms. Clifford believed he had breached the agreement. Mr. Cohen explained the FEC had sought his response to a complaint about the payment, according to people familiar with the call. Mr. Cohen has called the allegations in the complaint meritless.

Ms. Clifford asked her lawyer to contact California billionaire Tom Steyer, who is bankrolling an anti-Trump ad campaign, to ask if he would indemnify her, a person familiar with the discussion said. Mr. Davidson declined to make the call.

In late February, Ms. Clifford decided she wanted to blow up the deal and that Mr. Davidson wasn’t the man for a full-on confrontation, people familiar with the matter said.

Attorney Michael Avenatti in a television appearance. Photo: ABC News

She hired Mr. Avenatti, an aggressive, media-friendly Los Angeles lawyer who last year won a $454 million verdict in a lawsuit alleging fraud against Kimberly-Clark Corp. and its spinoff Halyard Health Inc.

Around the same time, Mr. Cohen obtained a temporary restraining order against Ms. Clifford in arbitration.

Mr. Avenatti then filed a lawsuit in Los Angeles County Superior Court asking a judge to declare the nondisclosure agreement invalid on the grounds that Mr. Trump didn’t sign it and Mr. Cohen had breached it.

Ms. Clifford, who has been drawing big crowds lately at strip clubs around the country, recently established a crowdfunding site to finance her legal battle. As of Tuesday evening, it had raised more than $270,000.

Write to Joe Palazzolo at joe.palazzolo@wsj.com and Michael Rothfeld at michael.rothfeld@wsj.com