On November 3, California voters will decide one of the most consequential and most argued-over measures in recent memory. Proposition 40 would require billionaires who lived in California on January 1, 2026 to pay a one-time state tax equal to 5 percent of their net worth, with 90 percent of the money directed to health care services.

You probably already have an opinion about that. Most people do. We’d bet that if you've formed your view mostly from headlines, ads, and social media posts, you haven't read the measure itself. You don't know who is funding each side and you may have missed a detail that could decide its fate no matter how the vote goes.

That's why we built the Prop 40 Tracker.

Voters are writing the law

California voters don't just elect lawmakers. They make law directly. That power dates back to 1911, when the Progressive movement added the initiative, referendum, and recall to the State Constitution. It's a remarkable amount of trust to place in ordinary citizens, and it comes with a responsibility the system has never fully solved: how do millions of busy people make informed decisions about complex legal text?

For over a century, the answer has been a patchwork of official voter guides, nonpartisan analysis, newspaper endorsements, and a flood of campaign advertising. The official sources are excellent and thorough. They're also long, scattered, and static. Campaign messaging, meanwhile, is fast, everywhere, and designed to persuade rather than inform.

We wanted to build something that combines the rigor of the first with the speed of the second.

Three promises

Everything in the tracker follows three rules.

Verbatim. When we show you what Prop 40 says, we show you the official text exactly as written. No paraphrase sits between you and the law, including ours.

Sourced. Every claim links back to where it came from, whether that's the Secretary of State's Voter Information Guide, the Legislative Analyst's Office, or campaign filings. If you don't trust us, you shouldn't have to. You can check.

Both sides. We present the strongest case each campaign makes, in their own words. We don't rank arguments, declare winners, or take a position on how you should vote. Our goal is for supporters and opponents alike to look at the tracker and agree that it represents them fairly.

Follow the money

A ballot campaign is also a fundraising contest, and knowing who is paying for the messages you see is part of understanding the race. California has led on this front for a long time. In 1974, a coalition of reformers backed by then-Secretary of State Jerry Brown put Proposition 9, the Political Reform Act, on the ballot, creating the most detailed disclosure law in the country. Before that law, there was no systematic way to check whether a campaign had reported all of its contributions and spending.

Fifty years later, that disclosure data is public, but it isn't easy to read. The tracker turns those filings into something you can actually follow, updated twice daily as new reports come in.

The detail most voters will miss

Here's an example of what a closer look reveals. Prop 40 isn't the only measure on the ballot that touches this issue. If Proposition 41 or 42 gets more yes votes than Prop 40, courts could find that they conflict, which means Prop 40 could be blocked even if a majority of voters approves it. That's the kind of context that rarely makes it into a 30-second ad, and it matters regardless of which way you lean.

What we're not doing

We're not telling you how to vote. We know a tracker built by a tech company, covering a tax on wealth largely built in tech, will get a second look from people on both sides. We welcome that. Hold us to our three promises, and if you find something that falls short, tell us at contact@capitol.ai

Try it

The Prop 40 Tracker is live today at prop40.usecapitol.com. Read the measure, see the race, follow the money, and make up your own mind.

Election day is November 3. Don’t forget to register to vote!