When California Governor Gavin Newsom vetoed a bill regulating artificial intelligence companies last month, many people in Silicon Valley rejoiced. Some of them also quietly thanked a man 3,000 miles away in Washington — Luther Lowe, the head of public policy for Y Combinator. Young tech companies usually can’t afford high-power lobbyists, but in hiring Lowe a little over a year ago, startup incubator Y Combinator recognized that most of them could use help in government. Lowe’s job is to advoc...