In his work, Mr. Pastor has drawn parallels between the political polarization of America today and 1990s California, when demographics were changing to become more Latino and when the state enacted harsh measures against immigrants.

Although California is today perceived as an inveterate, deep-blue state, the overwhelming control that Democrats currently have over both the legislative and executive branches is a historical anomaly. Since 1900, there have been nearly three times as many Republican governors in California as Democrats. And when Mr. Newsom succeeded Jerry Brown as governor in January it was the first time a Democrat had followed a fellow Democrat since 1887.

Now, however, momentum is clearly with the Democrats, as anger over Mr. Trump’s presidency has unleashed a legislative fervor.

Chris Lehane, a former political adviser to President Bill Clinton, said progressives in California were in the midst of a “renaissance in a belief in government.” He described Mr. Trump’s election as being the action that helped spur a liberal reaction — he called it “political physics.” Mr. Lehane said he was struck not only by the number of progressive laws coming out of Sacramento this session but by their breadth and ambition. “I think the tempo is really at a different level,” he said. “Now you see California playing offense.”

But he cautioned that the Democrats’ success, and their renewed faith in government, was predicated on government being able to solve the state’s many social ills — its lagging educational system and housing crisis, among them. “We live in a world where technology is moving so fast it’s really so difficult for society to adapt,” he said. “Is government able to move fast enough to be able to address these issues? And ultimately if government can’t, then who does?”

Tim Arango and Jose A. Del Real reported from Los Angeles, and Thomas Fuller from San Francisco.