More than $351 million in political donations has been poured into a high-stakes contest about a proposed wealth tax on the November ballot, making it one of the most costly campaigns in California history. About 90% of the money is being spent to defeat a statewide initiative to impose a new tax on the assets of billionaires, a multifaceted opposition effort bankrolled primarily by ultra-rich Californians being targeted by a measure that supporters call an economic reckoning.

The billionaire tax, Proposition 40, would levy a one-time, 5% tax on many assets of California billionaires who lived in the state as of Jan. 1. Millions of dollars continue to flow into the campaigns of three intertwined ballot initiatives at the center of the debate: Proposition 40, and Propositions 41 and Proposition 42, which would neuter the Proposition 40 through strategic, esoteric tax law changes. "The pro-40 campaign picked a fight and then came to that fight with a butter knife against a nuclear arsenal," said GOP strategist Rob Stutzman, who is not involved in any of the wealth-tax-related ballot measures.

"Because they're so well funded, in today's multifaceted media world, they are able to show up everywhere from network TV to inside video games. That is a very, very large advantage few campaigns ever get to have." But, Stutzman warned, money does not guarantee a win. In the most expensive ballot measure fights in California history, $463 million was spent on two gambling proposals 2022. The initiatives pitted some of California's most successful Native American tribes with gaming interests against gambling corporations, including online sports gaming companies DraftKings and FanDuel. Both side's measure failed.

The tax measure was crafted by Service Employees International Union-United Healthcare Workers West in response to federal healthcare funding cuts signed by President Trump last year that are expected to reduce California’s healthcare budget by $100 billion, burdening the state’s most vulnerable residents. "Trump’s 'Big Beautiful Bill' slashes healthcare funding, with major coverage cuts scheduled to hit after the midterms," said Suzanne Jimenez, the union's chief of staff. "More than 3 million Californians could lose their health insurance.

Hospitals and emergency rooms face closure. Patients will die unnecessarily when the care they need is no longer there. Proposition 40 is an emergency response to that looming disaster." The proposition's supporters raised $34.3 million, nearly all of it from Jimenez's union. The two other measures, Propositions 41 and 42, would nullify the billionaire tax if either receives more votes.

Proposition 41 supporters say the measure aims to cut wasteful government spending by requiring audits for new state special taxes and would bar new state taxes that exempt their revenue from a state spending limit. Backers of Proposition 42 argue it would prohibit new taxes on retirement holdings, individually owned assets and other forms of personal savings. Advocates for the billionaire tax say both are well-financed smokescreens to undercut Proposition 40.

Opposition campaigns to the wealth tax as well as the two countermeasures have received enormous donations from several of the state’s billionaires. But Building a Better California, the main funder of efforts to defeat the wealth tax, noted that its allies included Democratic and Republican politicians, prominent labor groups and business leaders. "It’s rare for such a broad coalition to unite around any single cause in California, but it reflects the potentially devastating impact of this measure on healthcare, education, and our state’s economy," the group said in a statement.

Among the largest donors opposing the wealth tax are billionaires Sergey Brin, a co-founder of Google who has donated more than $100 million to anti-wealth-tax efforts, and former Google leader Eric Schmidt and venture capitalist L. John Doerr, who each kicked in $40 million. Brin, Schmidt and Doerr did not respond to requests for comment.

The spending disparity also reflects a divide among Democrats and their allies, many of whom support wealth taxes, but argue that the way Proposition 40 was written is disastrous to California’s volatile budget, which is dependent on the state’s wealthiest residents. Jodi Hicks, chief executive and president of Planned Parenthood Affiliates of California, said that while her organization would support a nationwide or a California wealth tax, their primary concerns are about 40's impacts on the state budget and healthcare in the state.

"We are opposed to this particular proposal because we think it does more harm than good," she said, adding that after what her organization "faced last year having to scramble for dollars because of [federal funding cuts] we are committed to work with the stakeholders facing cuts and not harming the budget and finding revenue in a smart way."

The cash imbalance between supporters and opponents of the billionaire tax is vast. Those opposed to the measure raised $316.7 million, while proponents raised nearly $34.3 million. The supporters of the wealth tax spent nearly all of their money gathering signatures to place the measure on the ballot. They had $1.6 million on hand as of Oct. 17. Now, as voters cast ballots, their campaign appears reliant on public events and media coverage, such as of Sen. Bernie Sanders' (I-Vt.) recent rally in support of Proposition 40 in downtown Los Angeles.

“What you are showing people from coast to coast and all over is that, yes, we can take on the greed of the oligarchs,” he said, calling it the most important ballot measure in the country.

“Yes, we can create an economy and a government that works for all of us, not just the 1 percent.”Facebook creator and Meta chief Mark Zuckerberg was among the California billionaires Sanders name-checked in his remarks. After Zuckerberg told company leaders that he planned to leave the state to avoid his control over the company substantially reduced by being forced to sell enough of his stock in the social media giant to pay the proposed levy, the company on Wednesday announced the creation of a new, non-voting type of stock that would allow Zuckerberg to sell enough shares to pay the proposed tax while retaining his voting power in exchange for him agreeing to remain in the state for eight years.

The pro-wealth-tax campaign is sending voters emails and texts and has an online presence. “Remember: it’s not enough to vote YES on 40. You also need to vote NO on 41 + 42,” read an email sent to voters on Tuesday.

“Don’t be fooled: Props 41 and 42 are billionaire-funded initiatives designed specifically to undermine Prop 40, the California Billionaire Tax.”Meanwhile, the anti-40 and pro-42 campaigns are inundating voters on television, streaming services, in mailboxes, through online influencers and even in digital video games such as Sim City. Jimenez said voters will see through the blizzard of campaign messaging.

"The billionaires think voters are stupid. They think they can bury the facts under millions of dollars in advertising and disguise Prop. 42 ... as protection for ordinary taxpayers," she said. "Their spending also makes our case for us. When billionaires can afford to spend millions a day protecting their fortunes, voters can see that billionaires have plenty of money to spare." Sheri Sadler, a veteran Democratic media buyer, questioned how much voters were hearing about the rationale for the proposed billionaire tax.

"The yes side is severely lacking in getting their message through while the no side is dipping into different kinds of pockets," she said. Jessica Levinson, an election law professor at Loyola Law School, said that beyond voter confusion about the competing ballot measures, it is certain to face legal challenges, notably about the retroactive nature of the tax, which would apply to any billionaire who lived in California as of Jan. 1. She described that as "the biggest legal pressure point." "It's kind of a mess," she said.