It was late in the evening at a Christmas party hosted by crypto titan Chris Larsen — featuring singer Janelle Monáe and a towering abominable snowman with glowing red eyes — when Brin and his partner, Gerelyn Gilbert-Soto, confronted Newsom about a new proposal to tax billionaires in California, according to people who’ve spoken with the governor. Such a levy could hit Brin’s stake in Alphabet Inc. and his $272.6 billion fortune.

Newsom, who opposes the wealth tax, was still telling people about the lengthy exchange at the party months later, complaining of a lingering cold the pair had given him, according to the people, who asked not to be named discussing private conversations with the governor. 

Brin, meanwhile, followed through. He left the state, bought a lakeside mansion in Nevada, and started bankrolling a billionaire political uprising in California. 

Newsom through a spokesperson declined to comment on the interaction. “The governor has been very clear with everyone, no matter who they are, that this effort will do serious damage to the state, including for public safety workers and schools, at the expense of one special interest group,” Izzy Gardon, a spokesperson, said. A representative for Brin didn’t respond to requests for comment.

Brin’s political push reflects a broader awakening among California’s ultrawealthy. Over the past six months, the proposed billionaire tax and a heated governor’s race have drawn tech titans and business leaders more directly into the state’s affairs — a space many of them have traditionally kept at arm’s length.

Prior to this year, Brin’s last contribution in a California election cycle was 2010 when Arnold Schwarzenegger was governor and the Google co-founder largely backed climate causes. He’s now spent more than $58 million in the last four months, including an extra $9 million disclosed late Friday, but more importantly has helped mobilize a network of fellow tech titans in a push to sway state issues.

“The wealth tax was a wake up call, it was a fire that just lit up Silicon Valley literally in a matter of weeks,” said Steven Maviglio, a veteran Democratic strategist. “I’ve never seen anything like it.”

Altogether, ultrawealthy donors have injected more than $270 million into California’s political scene in this election cycle. Outside of the wealth tax, billionaire Tom Steyer is emerging as a top Democratic candidate for governor after the downfall of former Representative Eric Swalwell following allegations of sexual assault. Steyer, a former hedge fund manager, has spent more than $140 million in his election bid, crowding TV airwaves with ads and labeling himself a “class traitor” with a campaign modeled after Vermont Senator Bernie Sanders.

Ballots for the June 2 primary election start going out next week. Brin and a cohort of the ultrawealthy including Coinbase CEO Brian Armstrong and venture capitalists Vinod Khosla and John Doerr have plowed millions into supporting Matt Mahan, a Silicon Valley mayor, with a back-to-basics agenda and a penchant for taking on the state’s Democratic establishment. 

Read more: Billionaires Push Pick for Governor After Swalwell Scandal

That money has helped Mahan buy airtime and attracted controversy, but his polling numbers remain stuck in the single digits while Steyer’s well-funded progressive campaign is gaining favor with voters. Brin has also backed Republican Steve Hilton, who’s currently leading polls.

“You have two polar opposites going on. You have a billionaire running who has actually fully adopted an agenda that the vast majority of voters agree with: Taxing billionaires, funding healthcare, fighting back against ICE,” said Lorena Gonzalez, head of the state’s largest union group, the California Federation of Labor Unions. “And then you have billionaires pushing a candidate whose talking points are apologetic to the tech industry.”

The billionaire political activism in California mirrors larger shifts in Silicon Valley and the nation. President Donald Trump has given tech billionaires broad access to the White House, inviting Brin and other industry captains over for dinner and to join advisory boards. 

In California, Brin’s newfound political action was catalyzed by the wealth tax proposal, which would levy a one-time 5% tax on billionaires to help offset federal health-care cuts. In a Signal group chat earlier this year with other Silicon Valley elite, Brin floated the idea of raising hundreds of millions of dollars to influence California politics, according to a person who saw the message.

Brin left California for Nevada ahead of a Jan. 1 residency deadline for the proposed wealth tax, which still has to get enough signatures to qualify for the ballot. He moved to a $42 million mansion on the Nevada side of Lake Tahoe, featuring two glass-walled funiculars.

Shortly after leaving California, Brin contributed $20 million to a new group dedicated to fighting the tax and pushing pro-business policies, Building a Better California, making him the single largest contributor. He gave it another $37 million over the spring, as the group quickly started supporting a trio of anti-wealth tax measures that could nullify a billionaire tax if it gets passed in an election. 

Building a Better California “remains fixed on long-term reforms supported by most Californians: housing affordability, stable funding for education, infrastructure investments, and government accountability,” a spokesperson said.

Joining Brin in the effort were other billionaires, including former Google CEO Eric Schmidt, Stripe CEO Patrick Collison and venture capitalist Michael Moritz. Peter Thiel, who also left California ahead of the New Year’s Day deadline, gave $3 million to a separate committee opposing the wealth tax.

“They don’t trust California anymore,” said David Lesperance, a tax attorney who specializes in relocations and has helped move five families out of the state because of the wealth tax threat. 

Brin and his fellow billionaires helped push up the costs to gather the more than 870,000 signatures required to qualify a ballot measure. This forced the union behind the wealth tax, SEIU-UHW, to spend more on their efforts.

Read more: In California’s Wealth-Tax Fight, You Can Make $30,000 Collecting Signatures

“At the end of the day, it is just a couple billionaires,” said Suzanne Jimenez, SEIU-UHW’s chief of staff. “It is not the overwhelming number of billionaires in the state and they’re doing this to a state that has helped them generate massive amounts of wealth.” 

Other billionaires have bankrolled their own political initiatives, including Larsen, who set up his own network of influence groups with names like Grow California and Golden State Promise.

Read more: Billionaire Fights San Francisco’s ‘Stupid’ Tax on High CEO Pay

Many in Sacramento are skeptical that Brin and his fellow ultra-rich will succeed in swaying California state politics. They point to the failed candidacy of former eBay executive Meg Whitman, who spent around $144 million of her own fortune to become governor, or even venture capitalist Tim Draper’s longshot initiative to split California into six separate states.

“They’re trying to extrapolate from their own industry, which might have been fabulously successful, that they know something about political advertising, when they don’t,” said Garry South, a veteran Democratic strategist. “They think, ‘Hey, I’ve got money I can throw it around,’ and they don’t really do their homework.”

Political consultants describe their frustration with some wealthy tech donors, who often view their political giving through an investment lens, promising big checks and not following through if they don’t see momentum. That’s led to questions about whether the California billionaire activism would continue if Mahan’s governor bid fails and the wealth tax passes. 

Even Larsen, who’s worth around $13 billion, has expressed anxiety that not enough business leaders are stepping into politics. “It’s a lot of talk, and they’re happy, but we don’t see the firepower we need to take on the SEIUs,” he said, referring to the state’s largest union.

Newsom, for his part, acknowledges that many of the state’s wealthiest residents are willing to donate significant sums of money, but want to do it on their own terms and not through a tax.

“Some will never give a penny away,” he said at a Bloomberg News event in January, not long after his encounter with Brin in the treehouse. “Some I respect. Some I don’t.”