Among his many friendships with Republicans, Mr. Brown cherished his friendship with Earl Warren. When Mr. Brown defeated Richard Nixon to win re-election in 1962, he and Mr. Warren toasted the victory. When Mr. Brown lost four years later to Ronald Reagan, Mr. Warren was dismayed and wrote to his friend, “You have given our state good, progressive government for eight years and that is all any man could have done.”

Mr. Reagan also governed in the spirit of the Party of California. He campaigned as a tax-cutter, but he proposed the largest tax increase in the state’s history. He signed a law that legalized abortion and supported environmental initiatives that included creation of the Air Resources Board, which regulates emission standards.

Mr. Schwarzenegger, another movie star elected governor, circulated Mr. Starr’s op-ed among his senior staff as a road map for the new administration. Mr. Schwarzenegger faced more crises than triumphs during his seven years in office, but Jerry Brown credits his predecessor for initiatives that Governor Brown adopted and advanced, like the cap-and-trade program to curb greenhouse gas emissions, a high-speed-train route, tunnels to draw water from north to south and circumvent the fragile Delta, and juvenile justice reform.

Jerry Brown modeled his second act after leaders on Mr. Starr’s list like Hiram Johnson, Earl Warren and his father, whom he identified as the most successful governors, “the people who built the state, who were innovators and who were not ideologues or people who were pigeonholed into one partisan box.”

In January, Governor Brown used his final State of the State address to highlight bipartisan accomplishments: global warming initiatives, changes to the pension and workers’ compensation systems, a state water bond, the “rainy day” fund.

In a state that has become so reliably Democratic that people forget that only four Democrats have been elected governor in modern times, the fastest-growing segment of California voters is those who decline to enroll in any political party. The independent voters outnumbered Republicans for the first time this year, a reflection of both shifting partisan allegiances and the historically weak nature of political parties in California. Among the state’s youngest registered voters, independents outnumber Democrats. They are the potential heirs to the tradition that goes back to California’s Gilded Age philosopher Josiah Royce, who preached the philosophy of loyalty that guided Governors Johnson, Warren, Reagan and Brown, father and son.

The Party of California is part spiritual commitment to the idea that there is something special about this place, part pragmatic bow to the reality of governing the world’s fifth largest economy, a vast, diverse nation-state. Ever since California became the most populous state more than five decades ago, it has had more of almost everything: billionaires and homeless, agriculture and high tech, immigrants from almost any land. Republicans, a quarter of the registered voters, still number close to five million and dominate in districts that have sent to Congress prominent conservatives like Kevin McCarthy and Devin Nunes.