Who’s donating to the billionaire-backed group that has raised almost $300 million to fight the wealth tax?

A billionaire-backed political action committee has raised more than a quarter-of-a-billion dollars and has spent almost as much in the run-up to the November election as it attempts to defeat a first-in-the-nation wealth tax on the state ballot.

Building a Better California formed earlier this year as talk of a potential ballot measure to tax the state’s billionaires swelled. The group launched with an initial $35 million in donations to fund an expensive signature-gathering campaign that placed two initiatives aimed at neutering the tax on the same ballot. Now, with less than a month until Election Day, the group has raised $296.6 million and spent $276.6 million, state campaign finance reports show. Of that, $45 million was raised last week alone.

“The stakes for these people personally are much, much higher than even these large donations,” Thad Kousser, a political science professor with the University of California, San Diego, said.

Backed by SEIU United Healthcare Workers West, Proposition 40 would levy a one-time 5% tax on the state’s more than 200 billionaires to fund healthcare, food assistance and education-related programs that recently lost federal dollars as a result of cuts made in President Donald Trump’s “Big, Beautiful Bill.”

Prominent tech CEOs and investors whose net worths exceed ten figures and stand to pay millions — or even billions — if Prop. 40 passes make up Building a Better California’s 80-person donor list. Google co-founder Sergey Brin, who moved out of California last year because of the proposed tax, is the group’s top contributor, having shelled out $102 million through Oct. 3. Brin has emerged as this election cycle’s biggest spender following a 15-year hiatus from California politics, and is worth an estimated $263 billion, according to Forbes.

Other top donors to the group include venture capitalist John Doerr, who has given $40 million; former Google CEO Eric Schmidt, who has given $35 million; Stripe CEO Patrick Collison, who has given $33.1 million; and venture capitalist Vinod Khosla and Ripple Labs crypto executive Chris Larsen, who have both given roughly $12.5 million.

In August, Building a Better California released its ballot positions for seven different ballot measures, but nearly 93% of its spending has been concentrated around just three initiatives: the billionaires tax and the two countermeasures — Propositions 41 and 42 — that contain provisions that would void the wealth tax if either also passes and receives more yes votes.

The largest share, $103 million, has gone to a committee supporting Proposition 41, which would require the state auditor to review proposed special taxes before they’re placed on the ballot. Another $65 million has gone to a committee backing Proposition 42, which would prohibit new state personal property taxes. More than half of all dollars expended on Propositions 41 and 42 came before the June ballot measure deadline as the group paid individuals to gather enough signatures to qualify.

Building a Better California has also spent $88.5 million bankrolling the main opposition campaign to the billionaires tax. They’ve given much smaller sums to a pair of ballot measures that would authorize housing bonds as well as one that would overhaul the state’s landmark environmental review law.

Building a Better California spokesperson Abby Lunardini said in a statement that they believe the state’s “future depends on maintaining our economic competitiveness and making smart, accountable public investments that will improve affordability and quality of life for all Californians.” The group opposes Proposition 40 because “it will devastate the state’s budget, tax base and economy,” Lunardini added, and that it is “fighting for more transparency in government and stronger protections for people saving for retirement” with Propositions 41 and 42.

Between the three measures, Marty Wilson, a Republican political consultant and former California Chamber of Commerce official, said in an interview that “their first priority has to be the defeat of Proposition 40.”

“They’ve got two reform measures that don’t really have any funded opposition, so they can lighten up their spending on those,” he said.

There are no contribution limits for ballot measure campaigns in California, and battles between opposing sides of a proposition have often triggered spending in the tens of millions to hundreds of millions range. A pair of sports betting measures in 2022 set the record with more than $400 million expended. The current campaigns for Props. 40, 41 and 42 have spent more than $242 million this cycle.

Building a Better Bay Area so far has heavily out-raised its opponents. The healthcare union’s campaign in support of the billionaires tax has raised nearly $31 million as of Sept. 19. Another campaign set up to support Proposition 40 and oppose Propositions 41 and 42 has separately raised $340,000.

The money that the billionaire-backed group is pumping into California elections is likely the most of any PAC this election cycle — even from some of the state’s most powerful players. The California Business Roundtable Issues PAC, which has spent money supporting several initiatives including one that would make it more difficult to pass special taxes, has raised $7.8 million and spent $9.2 million this year as of Sept. 19. The California Teachers Association’s Issue PAC has comparatively raised and spent $29 million, and the California Democratic Party has raised nearly $28 million and spent $22.6 million.

Dave Regan, the president of SEIU United Healthcare Workers West, acknowledged in an interview last month that “there’s no question we can’t compete in terms of financial resources.”

Instead, they’re focused on recruiting as many volunteers as they can to combat what Regan referred to as an “avalanche of dishonest spending.” Sen. Bernie Sanders (VT-I) has also offered his progressive star power to the campaign, headlining rallies this past weekend in Los Angeles and San Francisco where he called it the “most important ballot initiative in the country.”

Polling for the billionaires tax and the two competing measures continue to be split as recent surveys have shown the measure hovering slightly above or slightly below the majority threshold.

With some voters still undecided, Kousser, the political science professor, said that Building a Better California’s spending “could tip the balance” if they’re able to make an effective argument.

“None of these billionaires could be the face of the campaign against Prop 40,” he said. “But that side is in the fortunate position where some of the biggest and best political brands in California politics are opposed to this — teachers, firefighters, police officers — so they have many groups, including many union groups, that have opposed this initiative. They are putting those voices front and center.”

Questions remain about how much impact Building a Better California will continue to have on state politics after the billionaires tax is settled in November, though the billionaire-backed group has shown no signs it will fold its tent after Election Day.

“They’re all invested here. They all have customers here, employees here,” Wilson said. “I think they feel duty-bound to protect the interests of their employees, their customers and their shareholders.”