California’s proposed billionaire tax has drummed up more than enough signatures to make it on the fall ballot. 

The milestone sets up a a high-stakes showdown with money from labor, political groups, and the tech industry likely to pour money into campaigns for and against the measure.

Backers of the initiative announced this weekend that more than 1.5 million people signed a petition to bring the one-time, 5% wealth tax to a statewide vote in November. That’s well beyond the 875,000 names needed to qualify the measure, and likely sufficient to account for illegible or invalid signatures. 

The Service Employees International Union United Healthcare Workers West, representing more than 120,000 healthcare workers, pitched the tax to make up for federal spending cuts that threaten to shutter hospitals (opens in new tab) and kick millions of people off medical insurance. 

“A very small group of the most controversial billionaires on the planet tried to stop Californians from being able to save their local emergency rooms and hospitals — but our current signature tally proves front-line healthcare workers will prevail in bringing this commonsense proposal to voters,” Billionaire Tax Now spokesperson and SEIU-UHW Chief of Staff Suzanne Jimenez said in a statement Sunday. “When our growing coalition files these signatures, David will have won the first round against Goliath, but healthcare workers and our allies won’t quit until we fully protect our patients from the looming healthcare disaster that will be caused by $100 billion in cuts to California healthcare.”

Proponents of California’s wealth tax estimate it would raise $100 billion in one-time revenue, even if some billionaires leave the state because of the measure. The nonpartisan California Legislative Analyst’s Office forecasts tens of billions in upfront revenue but cautioned that the tax could cost hundreds of millions or more a year if some billionaires move elsewhere.

The proposal, which needs a simple majority to pass, would apply to assets of people with net worth of $1 billion or more who lived in California as of Jan. 1. That means it would affect about 200 people, according to the SEIU-UHW.

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Gov. Gavin Newsom slammed the tax, saying it could push wealthy residents to leave the state. Google cofounders Larry Page and Sergey Brin were among a handful to leave before the proposed Jan. 1 deadline.

Though they’ve proposed other ideas to generate revenue for state coffers, none of California’s leading gubernatorial candidates support the billionaire tax.

Tom Steyer, a Democrat and hedge fund billionaire turned environmental activist, pitched the idea of levying new taxes on large corporations to make up for federal healthcare cuts. Rep. Katie Porter said she supports a similar approach to taxing corporations while also lowering taxes on working families. 

Former Health Secretary Xavier Becerra has said it’s unfair (opens in new tab)for billionaires to pay a lower tax rate but argued that a one-time levy isn’t the way to make up for it. San Jose Mayor Matt Mahan echoed Newsom in calling the billionaire tax a threat to innovation (opens in new tab).

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The union-led tax effort is financially outgunned by billionaires coming out against the measure. Opponents are fighting back with initiatives of their own — and they’re paying signature-gatherers $15 per name, raising the cost of the showdown. 

Brin contributed more than half of the $80 million collected in the first few months of the year by anti-tax group Building a Better California, according to state disclosures. Millions more came from former Google CEO Eric Schmidt and venture capitalist Michael Moritz, chairman of The Standard.

Schmidt donated at least a million to anti-tax group the California Business Roundtable, which also raked in $3 million from Palantir cofounder Peter Thiel and $500,000 from Ripple Chairman Chris Larsen.

But one of the state’s most prominent billionaires — the eight-richest person in the world — has broken ranks, espousing his loyalty to the Golden State whether or not it raises his taxes.

“I say to everybody, ‘Move to California, don’t leave,’” Nvidia CEO Jensen Huang said in a panel conversation (opens in new tab) this month at the Stanford Graduate School of Business. “It’s the highest taxes in the world, but it’s OK.” 

With a net worth of $167 billion, Huang would pay $8 billion under California’s wealth tax. 

Also on the panel was one of the biggest proponents of a wealth tax — one who’s trying to scale the idea on a national level. California Rep. Ro Khanna teamed up with Sen. Bernie Sanders of Vermont to cosponsor the “Make Billionaires Pay Their Fair Share Act.” The bill, which was introduced a couple months ago, would impose a 5% wealth tax on more than 1,000 billionaires based in the U.S.

Though the most populous state to mull a wealth tax, California isn’t the first. Washington state adopted a 9.9% tax on millionaires that takes effect in 2028. Maine passed a 2% income tax surcharge for millionaires. And New York City Mayor Zohran Mamdani is backing New York Gov. Kathy Hochul’s pied-à-terre tax for homes worth $5 million or more.