In the darkness of the Airbus 350, high above the Atlantic, almost every screen played romantic comedies or cartoons. Only one screen remained stubbornly switched off for the entire 11-hour flight: that of Gabriel Zucman, who was fine-tuning a "manifesto against the international oligarchy" on his laptop.

On Saturday, September 26, the French-American economist got up at 4 am in Budapest, where he had gone to help the new Hungarian government with a project for a wealth tax. He ran to avoid missing his connection in Paris. Upon landing in San Francisco, he was as fresh as a daisy. "I'm fired up! I can't wait to dive into the fight." We followed him for five days. Unaffected by jet lag, he went from conference to meeting, to interview, to filming messages that he planned to "bombard" social media with, helped by three comms people who fluttered around him.

The fight centers on Proposition 40, which Californians are set to vote on during the November 3 midterm elections. Voters must answer yes or no to a one-time 5% tax on total wealth – both professional and personal – of the roughly 250 Californian billionaires.

The money raised, estimated at $100 billion, is intended to save the health coverage of 3.5 million Californians, threatened by cuts imposed by the One Big Beautiful Bill, signed on July 4, 2025, by President Donald Trump. Backed by the SEIU-UHW (Service Employees International Union-United Healthcare Workers West) union – which collected the 875,000 signatures required to put it to referendum – Proposition 40 draws directly on the work of two French-American professors at the prestigious University of California, Berkeley: Zucman, 39, and Emmanuel Saez, 53, his mentor and friend.