The explosive but unproven allegations about President-elect Donald Trump and his purported ties to Russia originated with the work of a respected former British spy who was hired by Democratic operatives and who began sharing his findings last August, federal officials confirmed to ABC News.
One of those who eventually received a copy of the spy's secret report was Republican Sen. John McCain, who confirmed Wednesday he gave copies to the FBI director after receiving them last month.
"I did what any citizen should do," McCain said in an interview. "I received sensitive information and then I handed it over to the proper agency of government and had nothing else to do with the issue. I don't know if it's credible or not. But the information, I thought, deserved to be delivered to the FBI, the appropriate agency of government."
The allegations were incendiary -- that Trump had been secretly filmed in a luxury Moscow hotel and was compromised by the Russian government, and that aides to Trump on at least two occasions over the summer of 2016 held secret meetings with Russian government agents. The details became grist for a top secret security briefing to both President Obama and Trump last week. A senior intelligence official told ABC News the briefers walked through the allegations with Trump.
The man who gathered the information had a serious pedigree in intelligence circles - a retired British spy who later helped found a private intelligence firm. He had been stationed in Russia for years.
Trump opened his first press conference in six months Wednesday by blasting the contents of the report.
"For all the talk lately about fake news, this political witch hunt by some in the media is based on some of the most flimsy reporting and is frankly shameful and disgraceful," he said.
While much of the material in the report is virtually impossible to prove or disprove, ABC News has for months been investigating the allegations and discovered serious flaws in the information.
The memos claim Trump lawyer Michael Cohen was part of an "ongoing secret liaison relationship" with the Russians and met with them "in Prague in August 2016."
But Cohen told ABC News and his boss he has never been in Prague.
"He brings his passport to my office," Trump recounted. "I say, 'Hey, wait a minute.' He didn't leave the country."
The report given to the FBI also claims that Cohen's father-in-law was "a leading Moscow property developer" close to Putin.
But ABC News went to the address linked to the property developer in Moscow identified in the report as Cohen's father in law. A tenant at the luxury Moscow residence put ABC News in contact with the owner, who said emphatically that he had no connection to Cohen. He was reached at an Eastern European phone number. Cohen's father in law divides his time between New York and Florida.
Other allegations from the Democratic researchers revolve around Trump's travel to Moscow for a Miss Universe contest in 2013, and whether the Russians filmed him with prostitutes "to be able to blackmail him if they so wished."
Trump denied that today, saying he knows how to avoid Russia's spy tricks.
"I told many people, be careful, because you don't want to see yourself on television, cameras all over the place," Trump said, adding a parting reference to the most graphic elements of the claims about him. "I'm also very much of a germophobe, by the way, believe me."
Reevell reported from Moscow.
Former British Spy Gathered Unsubstantiated Intel on Trump, Officials Say