Congressman Michael Capuano has been racking up endorsements in his reelection bid against Boston City Councilor Ayanna Pressley. First, famed civil rights activist and Georgia Representative John Lewis threw his support behind the 10-term incumbent, then the Congressional Black Caucus Political Action Committee, whose endorsement is viewed as significant because race — Capuano’s white, Pressley’s African-American — could be an issue in the campaign.

But neither endorsement compares to that of Captain America. Actor Chris Evans, who plays the patriotic superhero in the blockbuster “Avengers’’ film franchise, happens to be Capuano’s nephew and showed up to support his uncle at a fund-raiser Thursday at the Fairmount Copley.

Evans, a Sudbury native whose mom is Capuano’s sister, spoke briefly at the event, mostly about his uncle’s commitment to blocking President Trump’s conservative agenda. Afterward, Capuano tweeted a picture of himself with his family, including Evans, using the hashtag #TeamCap.