Opponents of the proposal, including Google co-founder Sergey Brin, have raised more than US$205 million to defeat the measure, arguing it would drive wealthy residents out of California and erode state tax revenue. (EPA Images pic)LOS ANGELES: When Americans vote in next month's midterm elections, one question on the ballot in California could echo far beyond the state: should the ultra-wealthy pay a special tax on their fortunes?

The proposal would require California's roughly 200 billionaires to hand over 5% of their net worth that will mostly be used to fund the public healthcare system gutted by President Donald Trump, and on which around half of Californians depend.

Advocates hope the move would set a precedent for other parts of the country at a time of rising anger over surging inequality in the US, as the fortunes of tech titans like Elon Musk reach eye-watering levels.