California Gov. Gavin Newsom handily survived a recall election last fall by smearing his Republican opponents as Donald Trump toadies. While the recall didn’t defeat Mr. Newsom, it also didn’t make him politically stronger. Frustration with Covid lockdowns has receded, but anger over the state’s myriad other problems—crime, homelessness, lousy schools, high energy and housing costs and electricity blackouts, among other things—hasn’t waned. Disapproval of Mr. Newsom’s job performance, especially among independents, has risen since the recall.

Enter Michael Shellenberger, 50, a former Democrat running for governor as an independent. His political evolution resembles the cartoon recently tweeted by Elon Musk —a stationary guy in the center left of the political spectrum finds himself being pulled to the center right as his fellow liberals sprint the other way. A self-described “eco-modernist,” Mr. Shellenberger has plenty of company in the Golden State. Most Californians aren’t nearly as liberal as the state’s political class, but Republicans have struggled to win statewide in part because their anti-immigrant rhetoric and cultural conservatism have turned off Hispanics and young people. Mr. Shellenberger is testing whether a political moderate running on quality-of-life issues can break the progressive stranglehold on Sacramento. He needs to place second in the state’s jungle primary on June 7 to face off against Mr. Newsom head-to-head in November.

Mr. Shellenberger’s bid may seem a long shot. Independents don’t benefit from party infrastructure, endorsements and financing. His campaign has raised a mere $722,000. But California’s GOP is weak, and there are no well-known Republican candidates in the field. There hasn’t been public polling on the race, though Mr. Shellenberger says his internal polls show equally strong support among Republicans, Democrats and independents.

In California, conservative talk radio can have a greater reach than TV advertisements. Mr. Shellenberger has been a frequent guest on popular radio programs such as “John and Ken,” where he’s opined about the state’s homelessness, rising crime and crazy climate politics. Yet he isn’t a conservative firebrand, and that may work in his favor. He describes himself in a Zoom interview as a “bleeding-heart liberal when it comes to caring for the vulnerable, a libertarian when it comes to being passionate about freedom, but a conservative when it comes to taking care of our civilization.”