FRANCISCO — Billionaire opponents of California’s proposed wealth tax have spent more fighting it than they ever have on a political cause in the state, according to a POLITICO analysis.

A record $612 million from more than 70 current and former California billionaires is flooding this year’s state elections, nearly half of it for groups working to defeat Proposition 40, the wealth tax initiative on Tuesday’s ballot, POLITICO found.

The fight over Prop 40 has brought California’s wealthiest residents — many from its native tech industry — together in an unprecedented show of political coordination, the new data reveals. Tech leaders say the wealth tax has accelerated plans for broader political engagement this cycle, building networks that could be the foundation for future campaigns.

It’s a particularly striking display of unity from Silicon Valley’s notoriously hard-to-organize donor class. Google co-founder Sergey Brin is by far the well-funded opposition’s biggest benefactor, with former Google CEO Eric Schmidt, venture capitalist John Doerr, Stripe CEO Patrick Collison and crypto executive Chris Larsen also among those who have contributed the most dollars in trying to stop the billionaire tax.

The possibility of a tax on their assets has drawn more than $293 million from at least 30 California billionaires, the majority of whom made their fortunes in tech but otherwise span industries, from agriculture to real estate — as well as the political spectrum, from established Democratic megadonors to some Republican allies and first-time donors.

Frank Slootman, the billionaire board chair and former CEO of cloud data company Snowflake, said he only had a “moderate” interest in politics despite giving $5 million to an anti-Prop 40 group, arguing that the measure erodes private property rights and the state’s economic dynamism.

“This upends the most basic assumptions we have about being a taxpayer and a resident of a state,” said Slootman, who has no prior record of California campaign contributions. “I vote in most elections, that’s about it. This is not about politics for me — it is far more important than that.”The other half of billionaires’ spending this year came largely from Tom Steyer, a rare billionaire endorser of Prop 40 who bankrolled his own failed gubernatorial bid — the most expensive primary campaign in state history.

Even longtime strategists who have worked for statewide candidates and California’s costly ballot battles struggled to find a historical parallel for the coordination or scale of billionaire spending against Prop 40.

Rob Stutzman, a Sacramento political consultant whose past campaigns have involved a billionaire gubernatorial candidate and record-breaking ballot spending over sports betting, said that Silicon Valley leaders see Prop 40 as an “existential threat to tech in California” and the innovation that has taken root in the region for decades.

“Having to defend against a direct assault is a more unifying principle,” Stutzman told POLITICO. “They’re known for their pet issues that are harder to organize their peers around, but you can circle the wagons to protect yourselves. There is nothing that focuses similar-situated people.”Proponents of Prop 40 contend the measure is necessary to backfill federal health care cuts.

The last year billionaires in California came closest to spending at this level was 2010, when they dropped $147 million on state races and measures, according to POLITICO’s analysis — a total that’s just over half of what the current wealth tax proposal mobilized. Most of it was the result of billionaire Meg Whitman, a former CEO of eBay and Hewlett-Packard, self-funding her unsuccessful Republican campaign for governor.

Scott Ellis, a millionaire and Prop 40 supporter who formerly served as a senior director at HP, described the magnitude of billionaire spending to fend off the measure as “a completely different animal” than past examples of “a lot of money spent by a rich person to get themselves elected.”

“People with wealth and extreme wealth are getting much more brazen than they used to be,” Ellis told POLITICO. “These people have tremendous resources. They have an incredible range of choices to make, including choosing to oppose this kind of ballot measure.”Representatives for several billionaire opponents of Prop 40, including Schmidt, Larsen and agricultural titan Stewart Resnick, declined to comment on POLITICO’s findings.

Others, like Doerr, referred POLITICO to Building a Better California, a new Brin-led political operation that has become the primary vehicle for billionaire money against Prop 40.

The group defended the importance of its cause, arguing the measure would “permanently devastate” the state tax base and budget while undermining the health care funding it’s intended to patch.

“We are fortunate to be supported by entrepreneurs and business leaders who have built their businesses and created hundreds of thousands of jobs here, and who share a deep commitment to advancing policies that will improve quality of life for all and protect the state's economic, jobs, and innovation engine for generations to come,” Building a Better California spokesperson Abby Lunardini said in a statement.

Debru Carthan, vice president of the SEIU-United Healthcare Workers West union behind the billionaire tax, responded to the contributions, saying, “no amount of billionaire spending is going to intimidate us or turn us back.”Tech leaders have told POLITICO that the wealth tax awakened a sleeping giant in California politics: their previously disengaged industry peers, who months ago suddenly started spending across the ballot to steer California in a more moderate, business-friendly direction. The threat injected the wider political organizing, some of which preceded the measure’s introduction, with a new sense of urgency.

“The tech community has wanted to become a bigger player in California politics,” said veteran Democratic strategist Steven Maviglio.

“They're building an infrastructure, I think, for the long term because they've become a dominant player in our economy, and they now, after literally a decade of being hands-off, want to be very involved because they see the consequences,” Maviglio, who is working on a separate housing and environment-related ballot fight where Schmidt’s wife, Wendy Schmidt, has given $10 million, told POLITICO.

Earlier efforts to unify faltered amid strategic disagreements and overinflated fundraising promises. That was especially apparent in the push to rally Silicon Valley around San Jose Mayor Matt Mahan, a business-friendly candidate with a background in startups, during the California gubernatorial primary.

Although Building a Better California wasn’t spared its share of donor turmoil, an initial patchwork of opposition efforts eventually consolidated resources under the Brin operation’s strategy, devised with the help of veteran ballot-measure consultant Ned Wigglesworth.

The group also brought on fundraisers associated with California Gov. Gavin Newsom’s inner circle. Newsom has publicly opposed imposing a billionaire tax at the state level.

In addition to funding Prop 40 attacks, several billionaires claimed to have fled the state to avoid the tax. Brin, for example, registered to vote in Nevada. Because the one-time, 5% tax on assets would apply to billionaires who lived in the state as of Jan. 1, 2026, POLITICO’s analysis covers billionaires with recent California ties, based on information from Forbes, the progressive nonprofit Americans for Tax Fairness and news reports.

Some of those billionaires made their moves quietly, highlighting a split over how they should respond to the possibility of the tax passing.

“This has been a point of friction between me and some of my other billionaire friends,” Palmer Luckey, the billionaire founder of defense tech giant Anduril, said on a call with reporters this week. “They've said things like, ‘Palmer, you have to have solidarity for us. You can't enable these really bad policies. If you stay and if you don’t leave, it’s going to show them that there’s no consequences.’”Luckey, a vocal critic of the tax who hasn’t donated to the opposition campaign, added, “I'm planning on staying in California. I'm going to keep fighting it. I'm hoping that this doesn't pass.”

Meta revealed a plan last week incentivizing CEO Mark Zuckerberg to stay near the company’s Silicon Valley headquarters after the longtime California resident told a special committee of his board he was considering leaving over the tax. He also hasn’t challenged Prop 40 through political contributions.

DoorDash CEO Tony Xu, who poured almost $3.5 million into trying to prevent the wealth tax, was one of three members on the special committee negotiating with Zuckerberg.

Brin is single-handedly putting $102 million behind Building a Better California as it campaigns to sink Prop 40. This year, he’s also backed unsuccessful runs by Republican Chad Bianco and the moderate Mahan in the gubernatorial primary, plus Republican Steve Hilton’s campaign for governor. Federally, he’s given close to $450,000 to the Republican National Committee.

But before this cycle, Brin had been a sporadic donor, gone dark for many years. His last disclosed political donation in California was in 2010 — for $200,000 to join other Silicon Valley leaders in opposing an ultimately defeated ballot measure that would’ve suspended a state climate law.

Some of the billionaire donors — Slootman, Roblox CEO David Baszucki, Robinhood co-founders Baiju Bhatt and Vlad Tenev, Figma CEO Dylan Field, fintech executive Max Levchin and software founder Andrew Karam — have no history of spending on California politics before this year, according to state campaign records.

Tenev said in a statement that he donated to Building a Better California to support one of two other measures the group has advanced, which is designed to invalidate Prop 40 and would prohibit new taxes on various forms of personal savings.

“Special taxes on retirement and unrealized investment gains run contrary to the intent of the investment vehicles that have helped millions of Americans build wealth for the long term,” the Robinhood chief executive said. “History shows us that taxes aimed at a few have often been extended permanently to include more taxpayers over time." Another Building a Better California donor, Doerr, on the other hand, was a pioneer in shaping how Silicon Valley engaged with politics and Washington.

He co-founded TechNet in 1997, which launched a political action committee as a key part of its strategy. Today, the influential industry trade association manages both federal and state-level PACs on top of a vast bipartisan lobbying network, with Google, Stripe and Kleiner Perkins among its many corporate members.

The wealth tax has also brought former Sequoia venture capitalists, Michael Moritz and Doug Leone, onto the same side after they previously diverged on California’s partisan redistricting fight at the ballot last year. They spent $7.5 million and $100,000, respectively, on groups fighting Prop 40.

Leone is a prolific Republican donor who re-endorsed President Donald Trump in 2024, while Moritz has consistently criticized Trump and chided his supporters in Silicon Valley for making a mistake.

No less than a dozen of the billionaires spending on groups that oppose Prop 40 are current CEOs — including DoorDash’s Xu, Roblox’s Baszucki, Robinhood’s Tenev, Stripe’s Collison, Affirm’s Levchin, Schmidt of rocketmaker Relativity Space, Hemant Taneja of top venture capital firm General Catalyst, Field of design platform Figma and Parker Conrad of HR software provider Rippling. Collectively, they’ve plowed at least $88 million into their cause.

Several more of the billionaires in POLITICO’s analysis chair influential companies and firms. The opposition effort has received $40 million from Doerr, the Kleiner Perkins venture capitalist; $17.5 million from Larsen at the crypto company Ripple; and $2 million from George Marcus at the Bay Area real estate titan Marcus & Millichap — to name a few.

Whether the campaign infrastructure built by billionaires and the tech industry for the midterms will endure is still an open question.

Other new tech-funded groups this cycle have promised to play the long game and framed their plans around at least a decadelong horizon. Building a Better California itself has also committed to sticking around for the foreseeable future.

California political observers point to the size of the Brin-backed operation, as well as its decision to focus on additional environmental and housing measures, in predicting it won’t stop after the election.

Still, the unprecedented nature of their mobilization raises questions about what cause would be able to activate so many of these individuals again. Donors and advisers to Building a Better California previously clashed over whether spending on non-wealth-tax issues, such as environmental policy, could jeopardize the group’s success.

In the past, “if you look at those big dollar campaigns, ballot measure campaigns, those were funded in general by an industry,” said Jim Ross, a Bay Area-based Democratic consultant. “Wherein this, it's a bunch of individuals, very wealthy individuals, but they don't necessarily have any commonality other than they don't want to be taxed.”“When you have a group of wealthy people all putting money into this, a lot of the challenge is going to always be: How do you manage that coalition? How do you keep everybody moving in the same direction?” he added. One ready answer is a revived wealth tax effort.

Last week, Rippling CEO Conrad said in a social media exchange with Silicon Valley Rep. Ro Khanna, whose early support for the wealth tax alienated some of his original tech backers, that he "absolutely cannot afford to stay" in California — reasoning the measure may soon be followed by another one-time tax in the next election. Slootman made a similar calculation.

“In a one-party state with super majorities in both chambers, we are at risk for everything we own,” he said. “We are hunted animals in this state. They will be at it again in two years.”About this analysisPOLITICO’s analysis compiled records from the California secretary of state for 142 California billionaires that have contributed to state campaign committees, including 30 who had given to the following committees opposing Proposition 40: Building a Better California, Californians Against Tax Increases and Golden State Promise. Reporters reviewed donation records to verify names and employers matched with the billionaires who live in the state, as well as contacted each donor. Donations are as of Oct. 26.

Forbes estimated the wealth of the persons included in this analysis. Because billionaires often own properties in multiple states, we relied on Forbes to identify each person’s residence and supplemented with further data provided by the progressive nonprofit Americans for Tax Fairness. We included people who have recently left the state, including cases when they said they were leaving to avoid the potential wealth tax.