When California Gov. Gavin Newsom needed to fill the U.S. Senate seat of his late mentor Dianne Feinstein, he could have turned to a big-city mayor, a member of Congress or a powerful legislator. Instead, he chose Laphonza Butler, a former union leader and Democratic insider. She heads a national organization that raises money for women candidates who support abortion rights. She offered a loyal, familiar face who shares Newsom’s vision for a progressive California. In choosing Butler, he also elevated someone who could become an important ally for a potential national campaign that many see in his future.