SACRAMENTO, Calif. (AP) -- A major union announced a proposal Thursday to impose a one-time 5% tax on billionaires in California to address federal funding cuts to health care for low-income people.

Proponents, including the Service Employees International Union, hope to place the statewide measure before voters next year. The tax would be on the net worth of California's richest residents. A small portion of the money would also help fund K-12 education since the federal government has threatened to withhold grant money from public schools.

Backers of the measure sent a request to Attorney General Rob Bonta this week to get approval to start collecting signatures. The proposal would have to receive more than 870,000 signatures by next spring to qualify for the ballot in November 2026. If it qualifies, it's not guaranteed to pass. Democratic Gov. Gavin Newsom, for example, has opposed tax hikes in the past, including those specifically targeting the rich.

Proponents of the initiative said it was critical to backfill cuts to Medicaid because lives are at stake.

"If we do not do this, millions of people are going to lose health care, an untold number of people will go without treatment and there will be tragedy after tragedy," said Dave Regan, president of SEIU-United Healthcare Workers West.

Billionaires would have to pay for tax year 2026, and the money could start being appropriated in 2027. The tax would generate $100 billion in revenue for the state, backers say. The initiative says it's "designed to make the State tax system more equitable."

The big tax and spending cuts law President Donald Trump signed earlier this year will cut more than $1 trillion over a decade from Medicaid and federal food assistance.

The California Budget and Policy Center, a think tank in Sacramento, estimated the state could lose $30 billion in federal funding a year for Medicaid, which would result in up to 3.4 million people losing their coverage.

Newsom said earlier this month that people enrolled in Covered California, the state's health insurance marketplace, could see their monthly health care bills nearly double next year as a result of the spending cuts law.

"California has led the nation in expanding access to affordable health care, but Donald Trump is ripping it away," he said.

Proponents of the proposed ballot initiative say billionaires have an obligation to do their part.

"We hope that some and perhaps hopefully a large number of billionaires will recognize that it's important in the state where they've grown their fortune that they have a responsibility to society to preserve the future of California," said Emmanuel Saez, a professor of economics at the University of California, Berkeley.