The Quiet Voice in R.F.K. Jr.’s Ear: A Former Aide to the Clintons

In his outsider bid for the White House, Robert F. Kennedy Jr. is flanked by a team of unlikely political characters: new age health gurus, anti-vaccine activists, social media influencers, veterans of fringe third-party campaigns, cryptocurrency evangelists and militant environmentalists.

Jay Carson may be the most unexpected.

Now a Hollywood screenwriter, Mr. Carson, 47, has the résumé of a Democratic insider. He was the press secretary for Hillary Clinton’s 2008 presidential campaign. He worked for Bill Clinton, Chuck Schumer, Tom Daschle, Howard Dean and Michael Bloomberg. He describes Anita Dunn, a senior adviser to President Biden, as his political godmother and “one of my favorite people in the world.”

He left politics more than a decade ago for show business, becoming a producer on “House of Cards” and the creator of “The Morning Show.” He got divorced, got sober — he met Mr. Kennedy at one of his first 12-step meetings — remarried and settled into a new life in Topanga Canyon, Calif., with no plans to return to a campaign.

But over the past year, he has become a quiet, steadying force behind a candidate who is at war with the Democratic Party.

As an informal adviser, Mr. Carson has offered Mr. Kennedy encouragement and guidance on campaign staffing, communications and field operations. He produced and appeared in a 30-minute advertisement about Mr. Kennedy, paid for by a super PAC backing him. He was involved in running-mate discussions. Mr. Kennedy often texts him, “Please call Bobby,” and he does.