A billionaire former Democrat is making a splash with an $8 million contribution to California’s voter ID ballot measure — giving the campaign for strict voter security measures a last-minute financial push ahead of the November election.

Airbnb co-founder Joseph Gebbia donated Tuesday to the main committee backing Proposition 39, Californians for Voter ID. Prop 39, if approved by voters, would require California voters to show ID at the polls and other verification for mail-in ballots.

The donation would push Californians for Voter ID’s total cash on hand in September from $12.9 million to around $20.9 million now. Meanwhile, the four committees behind campaigns against Prop 39 had just $8.4 million on hand.

The Post reached out to Californians for Voter ID for comment.

Gebbia has donated to Democrats, such as Hillary Clinton and Joe Biden, in the past. But more recently, the wealthy tech entrepreneur has aligned himself with President Donald Trump, even taking a role with the Department of Government Efficiency.

Other prominent supporters of the pro-voter ID campaign include Nicole Shanahan, Robert F. Kennedy Jr.’s 2024 vice presidential candidate, and crypto titans Cameron and Tyler Winklevoss.

California Dems are rallying against the measure — as the No on Prop 39 campaign blasted the voter security measure as a “MAGA power grab” and attempt to “rig” elections.

Gov. Gavin Newsom is joining the “No on 39” side as an “honorary co-chair,” the campaign announced Wednesday.

Reed Hastings, co-founder of Netflix, and his liberal donor wife Patty Quillin have contributed $2.5 million to block the voter ID measure.

Newsom’s likely successor, gubernatorial candidate Xavier Becerra, and state legislative leaders have also been named honorary leaders of the opposition campaign.

The Post reached out to the governor’s office and political team on what Newsom’s role would actually entail. Newsom is planning to campaign aggressively against Prop 39.

“Trump and his MAGA allies tried to rig our elections once, and California voters shut them down with Prop 50,” Newsom said in a statement to Politico. “Prop 39 is just their latest attempt to silence us, because they know they can’t win in California in a fair fight.

The latest polls for Prop 39 show a tight race. According to a Sept. 21 to 24 poll by Mason-Dixon Polling, 49% of voters said they would vote “yes” while 42% said “no.”