Mr. Weaver and Mr. Longabaugh did not respond to requests for comment.

Mr. Longabaugh was a top architect of the 2016 Sanders campaign but parted ways one week into the 2020 effort, issuing a public statement with two fellow consultants, Tad Devine and Julian Mulvey ,that they were leaving “because we believe that Senator Sanders deserves to have media consultants who share his creative vision for the campaign.” The media firm eventually worked for Andrew Yang’s campaign.