Mr. Danchenko said the contact told him that Mr. Trump was “well known” to Russian security services and seemed surprised he had not already heard about the purported Ritz-Carlton matter.
A second contact also independently brought up a compromising video of Mr. Trump of a sexual nature that may have been covertly filmed at the Ritz-Carlton. However, that person did not mention urination, according to Mr. Danchenko.
Deciding to investigate further, Mr. Danchenko said he went to the Ritz-Carlton and chatted up a manager about rumors regarding celebrity visitors. The manager made a vague comment that security officials had covertly wired the hotel to gather compromising materials about important guests like Mr. Trump. Mr. Danchenko took it as corroboration.
“I circled around it, you know, enough for them to say, ‘look, yeah, there is a — you know, a funny thing. There might be a tape of Mr. Trump, might be sexual, but, you know, things that happen at Ritz-Carlton stay at Ritz-Carlton,’” Mr. Danchenko said.
Mr. Danchenko said he later spoke with a lower-ranking hotel employee who did “not say much,” but that he “interpreted as corroboration of what the first three told me.”
He declined to provide more details. When the F.B.I. spoke to him in January 2017 as it vetted the dossier, he told agents that the fourth source was a female hotel worker who said that “anything goes” there, adding that “officially, we don’t have prostitutes,” according to a bureau summary of the interview.
Mr. Danchenko also said he saw men at the hotel who looked like Russian security officers and women who appeared to be prostitutes, saying that the scene “sort of, to an extent, corroborates the story to me.”