Former top advisers to Senator Bernie Sanders are teaming up on a surprising new venture to try to rally progressive support for former Vice President Joseph R. Biden Jr.’s 2020 campaign: a super PAC.

Jeff Weaver, who served as Mr. Sanders’s campaign manager in 2016 and as a top adviser in 2020, is leading the effort, which will focus on mobilizing the base of Sanders supporters — young people, liberals Latinos and “blue-collar progressives” — for Mr. Biden.

Other top Sanders officials from the 2020 race who will be involved include Chuck Rocha, a senior adviser who focused on Latino outreach, Tim Tagaris, who oversaw digital strategy and fund-raising, and Shelli Jackson, a California strategist for the campaign. Mark Longabaugh, who worked for Mr. Sanders in 2016 but left the 2020 campaign early on, is also part of the new group.

Mr. Sanders has railed for years against super PACs, which can accepted unlimited donations, emphasizing his reliance on millions of small contributions from supporters online to fuel his two presidential bids.