The California Billionaire Tax Act is officially going to voters — and it isn’t alone.

After weeks of negotiations, the health care union sponsoring the measure announced Thursday that it had failed to reach a compromise with the state Legislature to remove the initiative from the ballot by a June 25 deadline.

A day earlier, the Secretary of State announced that two initiatives that would counter the Billionaire Tax Act had also qualified for the ballot, setting up a showdown come November.

In a defiant news conference Thursday afternoon, SEIU-UHW Vice President Debru Carthan said the union and its allies would continue to fight for the tax through Election Day in November.

“We’re here today to make it clear we aren’t backing down,” Carthan said. “The billionaire tax will be on the November ballot, and we intend to win.”

• The strange bedfellows lining up against the California billionaire tax

The highly controversial initiative would levy a one-time 5% tax on California’s approximately 250 billionaires in an attempt to offset funding lost from federal health care cuts.

In recent weeks, as negotiations over the initiative intensified, multiple unions, health care organizations, and affordable housing groups announced their opposition to the measure, claiming it would threaten future tax revenue by driving billionaires out of the state.

The measure also has serious money opposing it: Last week, the California Medical Association and California Primary Care Association put $100,000 each into a new group fighting the tax, which has since launched a statewide digital ad calling the initiative a “reckless wealth tax experiment.”

The two counter-initiatives headed to the ballot are the product of Building a Better California, a group funded by a coalition of billionaires including Google co-founder Sergey Brin, which has so far raised more than $100 million to oppose the tax and push other policy goals.

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Golden State Promise, a PAC funded by Ripple Executive Chairman Chris Larsen, has so far spent nearly $10 million opposing the measure, and said Thursday it intends to continue until Election Day.

Asked how much money SEIU had set aside to promote the Billionaire Tax Act, Suzanne Jimenez, the union’s chief of staff, said they were planning to raise money from supporters.

Proponents of the tax came down hard on Gov. Gavin Newsom in Thursday’s press conference, with Tax Act architect Dave Regan claiming the governor had “made clear he would not entertain any proposal to tax billionaires” — including a proposal to reduce the tax to 2%.

“Ironically, Gov. Newsom is in lockstep with Donald Trump and billionaires like Peter Thiel and Sergey Brin on this issue,” Carthan said, citing two of the most prominent billionaire opponents of the tax.

“So health care workers and working families across California are putting forward a long-overdue solution: making billionaires pay their fair share.”