In his first-ever bid for political office, former actor Ronald Reagan was elected governor of California in 1966, defeating two-term incumbent Gov. Pat Brown in a landslide. There was good reason for Democrats to fear that a radical right-winger had taken control of what even then was the nation’s most populous state. The onetime New Deal Democrat had become a very conservative Republican who often echoed the conspiratorial complaints of the John Birch Society. He regularly warned that social welfare legislation such as Medicare and Medicaid (“socialized medicine” to Reagan) and civil rights laws were going to lead to the...