Most of the important claims in the dossier — a series of reports written by Mr. Danchenko’s employer, Christopher Steele, a former British intelligence agent — have not been proven, and some have been refuted, including by Mr. Mueller. F.B.I. agents interviewed Mr. Danchenko several times in 2017 when they were seeking to run down the claims.
The first false statement charge in the indictment concerns Mr. Danchenko’s interactions with a person the indictment describes as a public relations executive with strong ties to the Democratic Party.
The indictment said Mr. Danchenko falsely told the F.B.I. that he had not discussed the claims in the dossier with the public relations executive. But, the indictment said, the executive — who in his professional career frequently interacted with Eurasian clients, with a particular focus on Russia — was a source for some of the claims, including gossip about the ouster of Paul Manafort as Mr. Trump’s campaign chairman.
The indictment did not name the person it called “PR Executive-1,” but its description matched the career of Charles Dolan Jr., who was the state chairman of the Clinton-Gore campaigns in Virginia in 1992 and 1996 and was appointed to a position in the State Department in the Clinton administration.
Mr. Dolan was earlier named in a declaration by Olga Galkina, one of Mr. Danchenko’s sources, as someone to whom Mr. Danchenko had introduced her; the indictment also said that the executive and a source who appears to be Ms. Galkina had regular interactions, including in ways that indicated they supported Mrs. Clinton’s campaign.
Mr. Dolan’s lawyer, Ralph D. Martin, confirmed in an email that his client was the executive named in the indictment, but said that Mr. Dolan, as a potential witness in the case, would have no comment.
The indictment linked Mr. Dolan to Mr. Danchenko in several other ways. It said he had lunch with Mr. Danchenko in Moscow in June 2016. At the time, Mr. Dolan was staying in the same Moscow hotel where the dossier claimed that Russian intelligence made a blackmail tape involving Mr. Trump and prostitutes.