• A wealth tax proposal in California would hit billionaires with a onetime 5% tax.
• A majority of voters say they'd support the measure, but critics argue it lacks sustainability.
• Gov. Gavin Newsom opposes the wealth tax, preferring higher taxes on California's top earners.

Americans really want wealth taxes. So far, they're not really succeeding.

The latest tax-the-rich proposal to make waves is in California, where billionaires like Mark Zuckerberg and Jensen Huang would pay a one-time 5% tax on their wealth. The tax would be based on their net worth at the end of 2026, and would hit any billionaires who were California residents at the start of 2026.

Already, the proposal has prompted alarm among the ultrawealthy and led to businesses moving out of the state entirely. Like other wealth taxes, it's popular among voters: A May 2026 survey by the Public Policy Institute of California found that 54% of likely voters support the billionaire wealth tax.

Now, some left-leaning groups are reportedly setting out to squash the tax before California's November ballot is set. According to the New York Times, they want a more stable revenue-raiser. That comes after the California Teachers Association decided that "this policy will not provide the sustainable and long-lasting funding that our schools and communities deserve."

Given the history of wealth tax proposals, their argument makes sense. Wealth taxes are difficult to implement; taxpayers can fight the validity of residency requirements or resurface arguments about their constitutionality. Jared Walczak, a senior fellow at the Tax Foundation, said that the tax "is constitutionally vulnerable on multiple fronts." Another persistent issue is around how wealth is assessed, or the maneuvers the ultrawealthy might take to shirk the tax — the Tax Foundation outlines a hypothetical where two high-value individuals avoid getting married, or decide to divorce, to bring their individual assets each below one billion.

All of that is part of a larger structural issue around taxation in the US. Billionaires and trillionaires generally don't accrue wealth in the same way that a regular salaried worker does. Most Americans are taxed primarily on their income, but the ultrawealthy often borrow against their assets without generating significant income. That means that every day Americans often pay a higher rate in taxes on their incomes than billionaires do. There's also a whole cottage industry devoted to helping the ultrawealthy move or reallocate assets in ways that shield them from taxes.

As its detractors note, the California measure, since it's a one-off tax on net worth in a certain year, only captures a moment in time. On the federal level, progressives like Sen. Elizabeth Warren have proposed measures like a flat annual wealth tax, which could bring in more consistent revenue. One solution that lawmakers have floated is hiking the top tax rates for the highest-earners, although that still wouldn't get at most of the wealth held by the country's billionaires and trillionaires. That might still be where California ends up, as the coalition of anti-tax left-leaning groups eyes making a temporary hike on higher earners in the state permanent.

California Governor Gavin Newsom has been vocally opposed to the wealth tax measure, although he's defended the state's higher taxes on top earners. He told the New York Times in January that the wealth tax is "something very, very different."

"I'll do what I have to do to protect the state," Newsom said.