Californian billionaires are reportedly spending millions on adverts opposing a proposed wealth tax.
Peter Thiel, one of the founders of PayPal and Palantir, and Sergey Brin, one of the founders of Google, are said to have contributed more than $100m (£74m) in a campaign to stop Proposition 40.
Under the proposition, also known as Prop 40, billionaires will have to pay a one-time state tax equal to 5 per cent of their net worth. The measure will be put to a vote in November.
Mr Thiel is reportedly backing a pro-business group called the California Business Roundtable (CBRT), which has launched a series of adverts attacking the plan.
One advert released on Tuesday by Californians Against Wasteful Spending and Higher Taxes, a group set up by the Thiel-backed CBRT, shows men and women in suits stealing household items such as TVs from regular Californians.
Chris Larsen, a crypto entrepreneur, has contributed $10m (£7.4m) to the effort, and L John Doerr, a venture capitalist and Google board member, has put in $7.5m (£5.5m), according to the Sacramento Bee.
Prop 40 is being supported by SEIU United Healthworkers West, a California healthcare union, and will impose a one-time 5-per-cent tax on California residents with a net worth of more than $1bn.
The union claims that the money will raise $100bn from 200 wealthy individuals to save California’s healthcare system, which has been severely affected by Republican cuts to Medicaid.
Mr Brin’s net worth is $275bn, meaning he could be forced to pay $13.75bn in tax if Prop 40 is passed.
A ‘Billionaire Tax Now’ rally took place in Los Angeles in February 2026 – Jason Armond / Los Angeles Times via Getty Images
Rather than being a tax on the wealthy, Prop 40 is an “everyone tax”, the advert says. The group claims that the tax could eventually be imposed on lower earners.
The largesse of the billionaires’ campaign contrasts with Prop 40’s supporters, who are spending just $4m on adverts.
Gavin Newsom, California’s governor, has said he opposes the tax, but it has been endorsed by the state Democratic Party.
A group called “No on 40”, which opposes the measure, claims California will lose $500bn in tax revenue from the six billionaires who have already left the state before the start of 2026, the cut-off for when they would be liable for the new tax.
A poll released earlier in August by UC Berkeley’s Institute of Governmental Studies showed that Prop 40 was supported by 48 per cent of likely voters and opposed by 41 per cent.