Prosecutors asked Mr. Mook about his role in funneling the Alfa Bank claims to the press. Mr. Mook admitted the campaign lacked expertise to vet the data, yet the decision was made by Mr. Mook, policy adviser Jake Sullivan (now President Biden’s national security adviser), communications director Jennifer Palmieri and campaign chairman John Podesta to give the Alfa Bank claims to a reporter. Mr. Mook said Mrs. Clinton was asked about the plan and approved it. A story on the Trump-Alfa Bank allegations then appeared in Slate, a left-leaning online publication.

On Oct. 31, 2016, Mr. Sullivan issued a statement mentioning the Slate story, writing, “This could be the most direct link yet between Donald Trump and Moscow.” Mrs. Clinton tweeted Mr. Sullivan’s statement with the comment: “Computer scientists have apparently uncovered a covert server linking the Trump Organization to a Russian-based bank.” “Apparently” is doing a lot of work in that sentence.

In short, the Clinton campaign created the Trump-Alfa allegation, fed it to a credulous press that failed to confirm the allegations but ran with them anyway, then promoted the story as if it was legitimate news. The campaign also delivered the claims to the FBI, giving journalists another excuse to portray the accusations as serious and perhaps true.