After more than 25 years leading Farallon Capital Management, Thomas Steyer is ready to launch into the next phase of his career. But he remains coy about what exactly he plans to do — perhaps because he plans to do a lot.

For the past few years, Steyer, an avid Democrat, has led a not-so-secret double life as a political power broker, education activist and energy policy commentator. The native New Yorker’s passion for his adopted home state of California burns so brightly that several of Farallon’s investors have speculated that he might run for office someday. But Steyer, who was a featured speaker at the Democratic National Convention in September in Charlotte, North Carolina, disavows any grand political ambitions — though that’s not to say he eschews a good dustup. Borrowing a saying from a friend, former secretary of State George Shultz, he says, “Democracy is not a spectator sport.”

The self-made billionaire is certainly much more than a citizen spectator. Steyer first ventured into California politics in 2010, when he cochaired and helped fund the campaign against a statewide ballot measure known as Proposition 23 that was supported by oil companies keen to roll back California’s greenhouse-gas emissions law. In 2012 he helped design Proposition 39, a ballot measure that sought to close a corporate tax loophole that had allowed out-of-state companies to choose how they calculated income taxes on their sales in California. Steyer spent $32.3 million of his own money to help bankroll the measure, which passed with a 61 percent “yes” vote in November.

Thanks to Steyer’s efforts, “39,” as it is known colloquially, is expected to raise $1 billion a year for the state, half of it slated to fund energy efficiency and clean-energy redevelopment projects in California schools and other public buildings for the next five years. The effort will not only provide much-needed construction jobs in California but also advance one of the causes closest to Steyer’s heart: energy conservation. A pragmatist to the core, Steyer is clear-eyed about the need to achieve greater energy independence by tapping into the U.S.’s vast shale oil and natural-gas reserves — hydraulic fracturing, he concedes, is here to stay — but he’s intent on encouraging responsible fracking and putting more resources behind new technologies to combat global warming.

“We’re just not dealing with it in a substantive way,” he says.

“It is like World War II — we’re just hoping that the terrible things happening elsewhere don’t happen to us. But we’re not isolated. Global warming is not something that you can deal with in between foreign policy and tax rates. This is your foreign policy. This is your tax rate.”

Steyer and his wife, Kathryn (Kat) Taylor, are so committed to raising awareness of alternative energy resources that they made a $40 million gift in 2009 to Stanford University, their alma mater, to establish the TomKat Center for Sustainable Energy, within the school’s Precourt Institute of Energy, to focus on and fund academic research into new technologies. In 2010 the Steyers made a $7 million gift to Stanford to create the Steyer-­Taylor Center for Energy Policy and Finance, an interdisciplinary center supported by Stanford Law School and the Graduate School of Business to study and advance innovative approaches to clean-energy policymaking. In 2011 they followed up those efforts by donating $25 million to Yale University to help launch the Energy Sciences Institute, another interdisciplinary research center.

Steyer is also willing to create his own organizations outside of academia to promote new ideas. In 2011, for example, he teamed up with his older brother James Steyer to launch the Center for the Next Generation, a nonprofit organization designed to function as an independent, nonpartisan contributor to major public policy debates on energy and education. The center, which concentrates on children’s issues and the environment, is currently planning a nationwide campaign, ironically titled Too Small to Fail, to raise awareness of the educational challenges U.S. children now face.

The freedom Steyer has gained by retiring from Farallon will allow him to dedicate much more of his time to the social and environmental issues he cares about most deeply, in California and beyond. His firm’s investors will be watching his next moves closely.

“I would not be at all surprised to see him remain engaged in California state-level politics or even get involved on a national level,” says Makena Capital Management partner Jeffery Mora. “Tom is a very smart, articulate individual who really walks the talk, and one of the things that has always impressed me is that he is willing to roll up his sleeves, get involved and go above and beyond.”