In 1996, a proposition was placed on the California ballot to make an addition to the state constitution: "The state shall not discriminate against, or grant preferential treatment to, any individual or group on the basis of race, sex, color, ethnicity, or national origin in the operation of public employment, public education, or public contracting," plus some supporting clauses. This was intended to stop affirmative action, especially in California's public universities. It passed with 55% of the vote.
In 2020, there was a proposition to repeal the additions made by Proposition 209. It failed, getting only 43% of the vote. So despite an apparent liberal shift in racial attitudes in the quarter-century between the propositions and a general desire to do something about racial inequality after the killing of George Floyd, the majority against affirmative action was almost the same (actually a little bigger in 2020). I've heard that when they're in doubt, people tend to vote against propositions, and since the presidential election got so much attention voters may not have followed Proposition 16 very closely. On the other hand, the proposition framed the pro-affirmative action position in a more attractive way--the short description in the official voter information guide was "allows diversity as a factor." In any case, the non-white share of the California electorate increased substantially between 1996, and California shifted towards the Democratic party--in 1996, Bill Clinton got 51% of the vote in California, only 2% ahead of his national share; in 2020, Joe Biden got 63%, 12% ahead of his national share. Given those changes you might reasonably have expected increased support for affirmative action.
The Field Poll was a long-running poll of California. It ceased operation in 2014, but the Institute for Governmental Studies at UC-Berkeley started one a few years later. Data from both the Field and IGS polls are at the UC-Berkeley Data Lab, so I got got one that asked about vote on Prop 209 and one that asked about Prop 16. A comparison of some groups is given below; I give the percent voting against affirmative action (yes on 209, no on 16).
Race/Ethnicity 1996 2020
White 64% 62%
Black 37% 31%
Latino/a 35% 53%
Asian 43% 56%
Vote:
Democratic 44% 36%
Republican 86% 96%
Perot 62%
Green 41% 28%
Education (whites)
No College 67% 80%
Some College 72% 71%
College Grad 57% 50%
Whites were about the same at both times. Blacks moved in favor of affirmative action according to this comparison, but the black subsample in the Field Poll is small and exit polls found only 26% of black voters in favor of Prop 209, so it's hard to be sure. Latino/a and Asian-American voters shifted against affirmative action, and majorities of both groups voted against Prop 16. The partisan divide was big in 1996, but even bigger in 2020. Among white voters, the educational divide increased, whith college graduates shifting in favor and people who didn't attend college shifting against.
Why didn't the apparent rise in concern with racial inequality lead to increased support for affirmative action? I think that it's because the big change in the last few years has been an increase in the number of whites who think that blacks face a lot of discrimination. But the natural conclusion from this is that we need stronger laws against discrimination or better enforcement of existing laws, not that we need affirmative action. The other important thing is the shift of Asian and Latino/a voters--if they'd voted the same way in 2020 that they had in 1996, it would have been close (my rough calculation is that Prop 16 would have won).