Facebook co-founder Dustin Moskovitz, Qualcomm co-founder Irwin Jacobs and Twilio CEO Jeff Lawson are joining the ranks of tech leaders throwing their support behind Proposition 15, a California ballot initiative that would raise as much as $12 billion for local schools and communities by hiking some commercial property taxes.

Until recently, Mark Zuckerberg and his wife, Priscilla Chan, were lonely voices in this fight, flooding the Yes on 15 campaign with more than $10 million in support. Despite activists' concerted efforts to get more of Silicon Valley's business leaders to support the measure, even the industry's most socially conscious CEOs were staying silent.

That is, until this week, when Salesforce CEO Marc Benioff announced he was backing the measure with $400,000 in funding. "We're supporting CA Prop 15 [...] because it's an important step in addressing the resource deficits that both our public schools & local governments face," Benioff tweeted.

That announcement broke the dam, leading to a wave of new contributions from the tech sector. According to newly filed contribution records to the Yes on 15 campaign, Moskovitz and his wife, Cari Tuna, donated $250,000 to the measure. Lawson and his wife Erica gave $100,000. Jacobs and his wife Joan contributed $250,000. And the Silicon Valley Community Foundation, which has raised gobs of money in the past from tech billionaires including WhatsApp co-founders Jan Koum and Brian Acton, shelled out $100,000. Moskovitz, Jacobs and Lawson are also all prominent Democratic donors.

"Support for Proposition 15 keeps rolling in because this crisis has further exposed the structural inequities baked into our current system, and tech and business leaders recognize that Proposition 15 will result in an equitable reinvestment in our schools, local communities, and small businesses," Gina Dalma, executive vice president at the Silicon Valley Community Foundation, said in a statement.

Proposition 15 will carve large commercial landowners out of California's Proposition 13, which allows property owners to pay taxes on the price of their property when it was purchased, not its current market value. Prop 13 has allowed commercial landowners in California to skirt the higher taxes that younger companies, many of them in the tech sector, currently pay. Proposition 15 would change that, and it has been endorsed by California Sen. Kamala Harris, a flurry of education and labor groups, and most mayors in the state. The opposition, meanwhile, includes a slew of business groups including the California Chamber of Commerce, as well as agricultural organizations, who argue that even though farmland is exempt from the measure, Proposition 15 would lead to tax hikes on "fixtures and improvements" to farmland.

Since Proposition 15 was introduced, a nonprofit group called TechEquity has also been actively seeking out tech sector endorsements for the measure. Catherine Bracy, executive director of TechEquity, was encouraged by the new show of support. "It's very heartening to see tech step up to support what is the most critically important policy to help California recover from the recession," Bracy told Protocol. "We hope this is an indicator that tech leaders realize the importance of addressing structural issues to bring about a twenty-first century economy that works for everyone."