A UC Berkeley Citrin Center–POLITICO poll finds support for Proposition 40 — a proposed 5% one-time wealth tax on California billionaires — has fallen to 45% from 50% in February, with 43% opposed and 12% undecided. Voters who say they are highly informed oppose the measure by 57% to 38%, and doubts about whether the tax would truly be one-time reduce support. Undecided voters lean strongly toward yes, while Gov. Gavin Newsom's public opposition appears to have weakened his standing with some Democrats. The online survey of 2,418 registered California voters was conducted Sept. 8–14, 2026 (±2.7%).
Poll: Support for California’s 5% Billionaires’ Wealth Tax Drops to 45%
California state flag flies on Oct. 24, 2022, in Sausalito, California. (Photo by Justin Sullivan/Getty Images)
A new UC Berkeley Citrin Center–POLITICO poll shows momentum slipping for Proposition 40, a proposed 5% one-time tax on the assets of California billionaires.
The survey of likely voters found 45% would back Proposition 40, 43% would oppose it and 12% remain undecided — a decline from February, when 50% supported the measure. The poll was conducted online Sept. 8–14, 2026, among 2,418 registered California voters and has a margin of error of ±2.7 percentage points.
Informed Voters Tilt Against the Measure. Among respondents who said they had heard a great deal about the proposal, opposition led 57% to 38%. That gap widened after the main opposition committee began running ads in August, highlighting questions about whether the tax would truly be a one-time levy.
“The campaign is just starting, and roughly a gazillion dollars are going to be spent on it,” said Jon Cohen, founder and CEO of polling firm TrueDot, which conducted the survey. “The fact that the people who are the most tuned in are the most opposed points to significant vulnerability that I think the yes side has.”
Support is more durable among groups less likely to oppose the proposal: undecided voters leaned heavily toward yes (65% yes vs. 15% no), and 66% of likely Democratic voters said they would support the tax. The poll also found 44% of respondents believe billionaires do more harm than good, compared with 34% who view them favorably.
Political Fallout. Gov. Gavin Newsom has publicly opposed Proposition 40. Pollsters say his stance appears to have damaged his standing with a segment of Democratic voters, creating an "issue-specific credibility" problem rather than a broader collapse, according to Cohen.
Analysts quoted by the Citrin Center suggested the contest may be decided among centrists and independents rather than strongly liberal Democrats, giving opponents an opening to stress perceived weaknesses in the measure and its long-term fiscal implications.
Bottom Line: While overall support remains close, the poll indicates vulnerability for supporters of Proposition 40 as better-informed voters trend against the measure and opponents ramp up advertising.
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