Billionaire developer Rick Caruso is breaking with California’s Democratic establishment by putting $25,000 behind a ballot measure that would require voters to show ID at the polls — marking new territory in one of the state’s biggest political fights.

Campaign finance records show Caruso — who spent more than $100 million to finish second in the 2022 Los Angeles mayor’s race — donated $25,000 on June 30 to Californians for Voter ID, the committee sponsoring the statewide initiative. Caruso’s donation comes as supporters have built a warchest of $3.38 million this year, according to The Post’s review of campaign filings. That is on top of $8.8 million raised last year.

The voter ID initiative would require voters to present government-issued identification when voting in person and provide identifying information for mail ballots, while also directing the state to provide voter identification cards upon request.

Republican Assemblyman Carl DeMaio, one of the state’s most outspoken advocates for voter ID requirements, praised Caruso for supporting the election security measure.

“As a prominent Democratic leader, Rick Caruso’s endorsement of Yes on Prop 39 reflects the strong bipartisan support that exists for Voter ID,” DeMaio told The Post. 

“Almost half of the signatures to put Prop 39 for Voter ID on the ballot came from Democratic and Independent voters and we expect the same bipartisan support to be reflected when Prop 39 overwhelmingly passes this November.”

The Californians for Voter ID committee reported raising $1.67 million through the first three months of the year, but momentum has been building in the spring and summer with an additional $1.71 million raised.

Caruso, who declined a request for comment, is pooling his money with a $1 million contribution from Steve Bray, a power magnate in Southern California, a $250,000 donation from venture capitalist Douglas Leone, and a $125,000 contribution from Stark Industrial LLC.

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Caruso’s contribution puts him at odds with Gov. Gavin Newsom and many of California’s Democratic leaders, who oppose the proposal as an unnecessary barrier to voting. Supporters argue the measure would strengthen election security and bolster public confidence in elections.

In 2024, Newsom signed a law prohibiting local governments from enacting or enforcing a voter ID requirement. The governor’s office did not immediately respond to a request for comment.

The fight in California comes as election integrity is expected to receive a national spotlight this week. President Trump said he plans to deliver a major address Thursday focused on elections, voting machines and election integrity, calling it “really big news.”

“It doesn’t get bigger because without free and fair elections, you don’t have a country,” Trump told reporters.

Trump has repeatedly cast doubt on the integrity of elections, without evidence, and he has specifically questioned the results in the Los Angeles mayor’s race. In a recent interview, the president said Spencer Pratt, a reality TV star and third-place finisher in the June primary election, was robbed a place in the November runoff.

“Spencer Pratt was an easy number two and maybe number one, but certainly number two,” Trump said. “And all of the sudden they had the mail-in ballots pour in and Spencer Pratt was gone.”

Trump himself has used a mail-in ballot to vote.

Trump’s remarks on Thursday are expected to touch on recently declassified intelligence related to past election investigations and what his administration describes as vulnerabilities in voting machines. Trump has been pushing for stricter election laws, including the SAVE Act, which would require proof of citizenship and photo identification during the voter registration process.

With more than $3.38 million already raised months before Californians cast their ballots, the issue of election integrity is shaping up to be one of the state’s most expensive and closely contested ballot fights.