A coalition of billionaires who could have to pay a proposed wealth tax in California has made its most significant move so far to undermine such a tax: It has reserved nearly $87 million of advertising time across the state to air TV commercials.

The ads, which will begin airing next month, are the opening salvo in what is expected to be an expensive fight that has already riven Silicon Valley and state politics.

A measure on the November ballot, Proposition 40, would assess a one-time tax on California residents with a net worth of at least $1 billion. The specter of the tax has already caused some of California’s wealthiest individuals to flee the state or to spend money on California political campaigns like never before.

Rather than directly oppose the initiative, the billionaire-backed coalition, Building A Better California, has gotten two of its own tax-related measures onto the ballot. Those measures contain provisions that could invalidate the billionaire tax if one of them also passes.

Building a Better California is backing Proposition 41, which would require audits of programs funded by new taxes, and Proposition 42, which would prohibit new taxes on personal property and financial assets. If both the billionaire tax and a countermeasure pass, the one that garners the most “yes” votes would prevail.

The group’s ads are expected to begin next month and will reach about $53 million in September, according to data from AdImpact. The final size of the ad campaign is likely to be much larger than the $86.9 million reserved so far, since the current buy includes only $3.7 million worth of ads in October, typically the heaviest month for political advertising.

Google co-founder Sergey Brin has put some $82 million into the committee, according to state records, and has emerged as the leader of the pushback effort, recruiting other Silicon Valley personalities to join his coalition. Other major donors include tech investors John Doerr and Michael Moritz.

The billionaire tax is sponsored by the Service Employees International Union-United Healthcare Workers West, which spent $31 million to get the measure on the November ballot. The union represents some 120,000 hospital workers who argue that the tax is necessary to offset healthcare cuts that President Donald Trump signed into law last year. The measure would require the state to spend 90% of the revenue from the billionaire tax on healthcare.

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This article originally appeared in The New York Times.

By Theodore Schleifer and Laurel Rosenhall/Mike Kai Chen
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