At the same time, some of the Jewish groups that have lobbied against the bill have acknowledged the complexities it is meant to address, while disagreeing that this bill is the proper vehicle for doing so.

“Many American Jews, and probably even more in California, are mostly secular, not religiously observant,” the Sacramento chapter of Jewish Voice for Peace wrote in a statement. “If asked offhand, many of us might say we identify as culturally and/or ethnically Jewish. But we vehemently oppose SB 1387 for its wrong-headed oversimplification of identity, one that could well exacerbate antisemitism, among other unintended consequences.”

The bill, the group contends, risks flattening rather than broadening public understanding of Jewishness by compressing Jews into a single ethnicity. (Supporters counter that the box is voluntary and can be checked in conjunction with any other identity boxes.)

“I consider myself a Jew ethnically, but there are many different ethnicities,” David Mandel of Jewish Voice for Peace told the California assembly’s judiciary committee on June 9. “This ill-considered bill, very expensive bill, will not add any useful information for the state and would end up costing millions.”

Mr. Stern is comfortable with the opposition. “That’s what it is to be a Jew, in some ways,” he said. “Being really comfortable with tension, and being comfortable with paradoxes, and understanding that we’re a people, we’re a nation, we’re an ethnicity, we are a religion, too. We don’t fit naturally. And that’s why we’re such a pain.”

Laughing, he added: “It’ll give a lot of grist for people to argue at over kitchen tables, as we have been doing for over 3,000 years.”