When the F.B.I. interviewed Mr. Danchenko in 2017, he told the bureau that he thought the tenor of the dossier was more conclusive than was justified; for example, Mr. Danchenko portrayed the blackmail tape story as rumors and speculation that he was not able to confirm. He also said a key source had called him without identifying himself, and that he had guessed at the sourcexe2x80x99s identity. The indictment accuses Mr. Danchenko of lying about that call and of concealing that a Democratic Party-linked public relations executive was his source for a claim about Trump campaign office politics.

Did the F.B.I. open the investigation because of the dossier?

No. Mr. Trump and his allies have insinuated that the F.B.I. based the Russia investigation on the dossier. But when counterintelligence agents launched the effort on July 30, 2016, they did not yet know about the dossier. An inspector general report established that Mr. Steelexe2x80x99s reports reached that counterintelligence team on Sept. 19, 2016.

The basis for the investigation was instead that WikiLeaks had disrupted the Democratic National Convention by releasing Democratic emails believed to have been stolen by Russian hackers, and that an Australian diplomat said a Trump campaign foreign policy adviser had bragged to him about apparent outreach from Russia involving an offer to help the campaign by anonymously releasing information damaging to Mrs. Clinton.

Did the F.B.I. take any investigative step based on the dossier?

Yes. The F.B.I. took the dossier seriously based on Mr. Steelexe2x80x99s reputation, and used some of it xe2x80x94 without independent verification xe2x80x94 for a narrow purpose that led to a dead end and became a political debacle. It included several claims from Mr. Steelexe2x80x99s memos in applications to wiretap Carter A. Page, a former Trump campaign foreign policy adviser with ties to Russia. In 2019, the Justice Departmentxe2x80x99s inspector general sharply criticized the F.B.I. for numerous flaws in those wiretap applications.

While the dossier-tainted wiretap of Mr. Page has received significant attention, it was a small part of the overall investigation, which issued more than 2,800 subpoenas, executed nearly 500 search-and-seizure warrants, obtained more than 230 orders for communications records, made 13 requests to foreign governments under mutual legal assistance treaties, and interviewed about 500 witnesses. Mr. Page was not charged with a crime, and only a handful of the 448 pages in the Mueller report focus on him.

Did investigators rely on the dossier for their findings?

No. The Mueller report does not present claims from the dossier as evidence, and many of the issues focused on by investigators did not come up in the dossier.

The dossier makes no mention, for example, of a July 2016 meeting at Trump Tower between Russians and senior campaign officials including Donald Trump Jr., who eagerly accepted the request for a meeting after being told they were bringing dirt on Mrs. Clinton.