The polygraph results came to light as pressure mounted on the president, with an ex-Playboy model suing to be released from another non-disclosure agreement while a former reality star alleging sexual assault took him to court for defamation.
Daniels, who alleges the affair took place in 2006, took to Twitter to warn she was "not going anywhere" despite a legal battle to stop her speaking out, and referenced her sexual encounters with Trump.
"Technically I didn't sleep with the POTUS 12 years ago. There was no sleeping (hehe) and he was just a goofy reality TV star," she tweeted, accusing Trump of bullying her and breaking the law to cover up the affair.
Her lawyer, Michael Avenatti, tweeted a picture of his client strapped to a chair taking the exam, with the hashtag #searchfortruth.
The Wall Street Journal reported that the lawyer paid $25,000 for the video of 39-year-old Daniels - real name Stephanie Clifford - answering questions as she was strapped to the polygraph.
A report on the test, commissioned as part of a 2011 interview published only recently by gossip magazine "In Touch," says Daniels was being truthful when she said she had unprotected sex with Trump in July 2006.
Legal jeopardy
The examination did not, however, corroborate the actress's allegations that the real estate mogul promised to include her on his reality show "The Apprentice."
Lie detector tests are generally not admissible in court because their accuracy is regarded as unproven.
The White House and Trump's lawyer, Michael Cohen, have repeatedly denied the affair with Daniels, although the attorney admits paying her $130,000 of his own money under a confidentiality agreement.
The Republican president will be vulnerable to accusations that he violated election law if the payment, plus allegations of cash given to silence other alleged mistresses, are considered attempts to sway the November 2016 election.
Ex-playmate Karen McDougal filed a lawsuit alleging a 10-month affair with Trump in 2006 and 2007 and petitioning to be released from a non-disclosure agreement with the National Enquirer, which paid her $150,000 for her story but then shelved it.
McDougal complained in documents filed in Los Angeles Superior Court that American Media Inc (AMI), which owns the Enquirer, misled her about the 2016 deal, rendering it invalid.
The President has repeatedly accused McCabe and former FBI chief James Comey of having protected Hillary Clinton. Source: AAP
"Ms McDougal received $150,000 -- nearly half of which went to the lawyer, who she did not realize was colluding with the other side -- and a false promise to jumpstart her career as a health and fitness model," the complaint alleges.
Threats of financial ruin
The suit argues that despite the relationship and the cover-up being "open secrets," AMI has pressured McDougal to ignore queries from prominent journalists about the relationship.
"They threaten her with financial ruin if she does not remain 'loyal,'" court papers say.
"AMI, meanwhile, feeds those same reporters false information about Ms McDougal, her relationship with Mr Trump, and its own machinations to bind her to silence."
In another blow for the White House, a New York judge allowed a lawsuit by Summer Zervos, a former candidate on NBC's "The Apprentice," to go ahead, rejecting a request for dismissal.
Zervos, who accuses Trump of defamation, says he fondled her and tried to forcefully kiss her in 2007.
She is among at least 16 women who have accused the president of varying inappropriate behavior, from harassment to sexual assault, all coming forward before or during his White House bid.
Trump has denied wrongdoing in all cases, and his campaign team published the account of a cousin of Zervos berating her for publicity-seeking.
Zervos responded by hauling Team Trump before the New York State Supreme Court in January 2017, citing "false and defamatory statements."
