Support for a one-time tax on California billionaires is slipping, according to the latest poll by the Berkeley Institute for Governmental Studies.
The erosion of support for the measure, Proposition 40, from 48% in mid-August to 43% a month later increases the likelihood that it won’t be approved, the pollsters concluded. The proposition is supported by many legislators and labor leaders, but opposed by Gov. Gavin Newsom and San Jose Mayor Matt Mahan.
The poll was conducted two weeks before ballots are to be distributed to voters statewide.
At the same time, another wealth tax measure, Proposition 3, that would make permanent an existing tax on high income earners holds a solid 20-point lead in the Berkeley poll.
Voter opinions on Proposition 40 are divided with 45% supporting its passage, while nearly as many (42%) are opposed.
By contrast, Proposition 3 is backed by a wide 20-point margin, with 54% of voters intending to vote Yes and 34% saying they will be voting No.
The latest Berkeley Institute of Governmental Studies Poll, announced today, asked California likely .
voters their voting preference on seven of the 14 state propositions to appear on the November election ballot by presenting voters with the verbatim text of the titles and summaries along with the major backers and opponents of each measure.
The poll also finds more voters now lining up against Proposition 39, the voter ID initiative than did so in August. It currently trails by a 13-point margin (52% to 39%) compared to a somewhat smaller 9- point deficit in August.
The poll also probed voter reactions to Proposition 40’s two counter initiatives, Propositions 41 and 42, placed on the ballot by opponents of the billionaires tax. The results indicate that while supporters outnumber opponents on both counter measures, neither receives majority support and large proportions are undecided.
Another tax-related ballot measure Proposition 43 to increase the vote threshold required to approve local special taxes from a simple majority to a two-thirds vote is trailing in the Berkeley poll by a 9-point margin. At present 40% say they would vote No, 31% would vote Yes, with a large proportion (29%) undecided.
Many voters (30%) are also undecided when asked about Proposition 4 to repeal the state’s current prohibition on offering public funding of candidate election campaigns. Voting preferences are currently evenly divided with 35% intending to vote Yes and 35% voting No.
The latest Berkeley IGS Poll was conducted online September 15-20, 2026, in English and Spanish among a random sample of 4,512 Californians considered likely to vote in the upcoming November statewide elections. Funding for the poll was provided in part by the Los Angeles Times and the Evelyn and Walter Haas, Jr. Fund.
“The findings suggest tough news for Proposition 40 proponents, said IGS Co-Director G. Cristina Mora. “With less than 50 percent support this close to the election, ballot measures for new taxes tend not to pass, as undecided voters likely break towards ‘no.’ “
“Unless we see meaningful pushes in marketing and canvassing aimed at reaching younger voters, and others who often stay home during midterm elections, the climb looks quite steep,” she wrote in announcing the poll results.
“At the same time, canvassing against Proposition 39 has seemed to successfully link the initiative to the Trump agenda and this has made the proposition less likely to pass.”
“Large partisan differences characterize support and opposition to Proposition 40, with Democrats supporting it greater than three to one, while Republicans are opposed nearly eight to one,” reported Mora. “The views of non-partisan voters are similar to those of the overall electorate. Yet Yes side support for the proposition has declined five points among its primary backers, both Democrats and non-partisans, since August.”
Support for Proposition 40 varies considerably by age, with twice as many voters under age 30 (68%) on the Yes side than voters 65 or older (34%). The poll also revealed a gender gap in voting preferences with female voters favoring the initiative while males are opposed. Voters of color are also more supportive of Proposition 40 than whites.
While both of Proposition 40’s counter initiatives hold small leads, neither receives majority support and large proportions are undecided The two counter initiatives to Proposition 40 placed on the ballot by its opponents hold early leads in the latest poll but neither receives majority support with many voters undecided.
