By Paul Wood BBC News, Washington
12 January 2017
Donald Trump has described as "fake news" allegations published in some media that his election team colluded with Russia - and that Russia held compromising material about his private life. The BBC's Paul Wood saw the allegations before the election, and reports on the fallout now they have come to light.
The significance of these allegations is that, if true, the president-elect of the United States would be vulnerable to blackmail by the Russians.
I understand the CIA believes it is credible that the Kremlin has such kompromat - or compromising material - on the next US commander in chief. At the same time a joint taskforce, which includes the CIA and the FBI, has been investigating allegations that the Russians may have sent money to Mr Trump's organisation or his election campaign.
Claims about a Russian blackmail tape were made in one of a series of reports written by a former British intelligence agent, understood to be Christopher Steele.
As a member of MI6, he had been posted to the UK's embassy in Moscow and now runs a consultancy giving advice on doing business in Russia. He spoke to a number of his old contacts in the FSB, the successor to the KGB, paying some of them for information.
They told him that Mr Trump had been filmed with a group of prostitutes in the presidential suite of Moscow's Ritz-Carlton hotel. I know this because the Washington political research company that commissioned his report showed it to me during the final week of the election campaign.
The BBC decided not to use it then, for the very good reason that without seeing the tape - if it exists - we could not know if the claims were true. The detail of the allegations were certainly lurid. The entire series of reports has now been posted by BuzzFeed.
And the former MI6 agent is not the only source for the claim about Russian kompromat on the president-elect. Back in August, a retired spy told me he had been informed of its existence by "the head of an East European intelligence agency".
Later, I used an intermediary to pass some questions to active duty CIA officers dealing with the case file - they would not speak to me directly. I got a message back that there was "more than one tape", "audio and video", on "more than one date", in "more than one place" - in the Ritz-Carlton in Moscow and also in St Petersburg - and that the material was "of a sexual nature".
One Russian specialist told me that Vladimir Putin himself sometimes says there is kompromat on him - though perhaps he is joking. The specialist went on to tell me that FSB officers are prone to boasting about having tapes on public figures, and to be careful of any statements they might make.
A former CIA officer told me he had spoken by phone to a serving FSB officer who talked about the tapes. He concluded: "It's hokey as hell."
Mr Trump and his supporters are right to point out that these are unsubstantiated allegations.
[The problem for compulsive liars is that even when they are telling the truth, we will doubt them because of their habitual behaviour.]•••••
The claims of Russian kompromat on Mr Trump were "credible", the CIA believed. That is why - according to the New York Times and Washington Post - these claims ended up on President Barack Obama's desk last week, a briefing document also given to Congressional leaders and to Mr Trump himself.
Mr Trump did visit Moscow in November 2013, the date the main tape is supposed to have been made. There is TV footage of him at the Miss Universe contest. Any visitor to a grand hotel in Moscow would be wise to assume that their room comes equipped with hidden cameras and microphones as well as a mini-bar.
At his news conference, Mr Trump said he warned his staff when they travelled: "Be very careful, because in your hotel rooms and no matter where you go you're going to probably have cameras." So the Russian security services have made obtaining kompromat an art form.
[By now everybody should be aware of how useless Trump's denial is. He lies continually.]
In a New York Times op-ed in August, the former director of the CIA, Michael Morell, wrote: "In the intelligence business, we would say that Mr Putin had recruited Mr Trump as an unwitting agent of the Russian Federation."
Agent; puppet - both terms imply some measure of influence or control by Moscow.
Michael Hayden, former head of both the CIA and the NSA, simply called Mr Trump a "polezni durak" - a useful fool.
The background to those statements was information held - at the time - within the intelligence community. Now all Americans have heard the claims. Little more than a week before his inauguration, they will have to decide if their president-elect really was being blackmailed by Moscow.