The race to be California’s next governor entered a new chapter this week. Toni Atkins, a veteran lawmaker with decades of influence in Sacramento, has stepped aside. In her place, Ian Calderon, bringing the restless energy of a 39-year-old millennial eager to reimagine the state’s future, has jumped into the contest. The shakeup reflects both the end of one political era and the beginning of another, setting the stage for what promises to be one of the most exciting primaries in recent California history.