Billionaire Tom Steyer has emerged as a frontrunner in the race for California governor, in no small part because of the millions of dollars of his own money that he's spent on ads before we've even had a primary.

On Tuesday, Steyer was given either a boost or a hindrance, depending on where you stand, by getting the endorsement of former state legislator, SF mayor and longtime candidate whisperer Willie Brown. As the Chronicle reports, the 92-year-old Brown has officially thrown his support behind Steyer, for better or worse.

"In my more than six decades in public life, I have had the opportunity to meet with many individuals seeking public office, taking time to understand their ideas, their judgment, their depth, and their ability to lead," Brown said in a statement. "After doing exactly that in this contest, I am proud to endorse Tom Steyer for Governor of California."

Brown likes to back a winner, and Steyer is certainly looking like that, particularly if this ends up being a two-man race between him and Republican Steve Hilton — with California only electing one Republican, Arnold Schwarzenegger, in the last 27 years, and that was mostly because he was Arnold Schwarzenegger.

Steyer offered his own thank-you statement complimenting Brown, saying, "California’s progress has always been shaped by leaders who understood how to turn bold ideas into action and deliver for working people. Willie Brown helped define that tradition through decades of public service, breaking barriers as the longest serving Speaker of the California State Assembly and as San Francisco’s mayor."

Steyer added, "His support reflects a shared commitment to service, effective governance, and pragmatic, ambitious leadership. I am grateful for his confidence as we work to move the state forward."

But even if this is Steyer's primary to lose, he still could face a significant challenge from former California Attorney General Xavier Becerra — who went on to serve in the Biden adminstration as Secretary of Health and Human Services — who has been rising in the polls in recent weeks. And we shouldn't discount former Congresswoman Katie Porter, who was an early frontrunner in the race in the pre Eric Swalwell days, due to her name recognition.

Challenges from those candidates are likely to include, as some attack ads have shown, harping on Steyer's status as a billionaire and where much of his wealth came from.

While Steyer spins his story saying that yes, he made his fortune at a hedge fund with fossil-fuel ties, he walked away from all of that over a decade ago in order to "focus full-time on fighting climate change." But a New York Times piece today suggests that the degree to which Steyer's wealth is or is not divorced from that former company, Farallon Capital, is not at all clear.

The official word from Steyer's campaign is that Steyer is only a "passive investor" at Farallon Capital these days, and "Employees at Farallon screen out any fossil-fuel-related holdings from his portfolio, and he no longer earns a share of the profits from the fund."

But the Times piece highlights the degree to which Farallon has sought out investments in coal businesses while other funds have backed away from them — leveraging their pariah status for their own gain. And a Farallon fund that appeared on Steyer's 2024 tax return had been used a decade ago for a coal-related deal.

The company continues to invest in the industry, bailing out an Australian coal terminal operated by Indian conglomerate Adani Group, which the Times notes is "a huge user of coal."

Still, supporters say Steyer has walked the walk in his environmental activism, making significant green investments in recent years.

Four years ago, as the Times reports, Steyer co-founded a firm called Galvanize, which funds green-energy projects, and he also bankrolls the partly climate-focused NextGen America.

Progressive groups like Our Revolution, founded by Senator Bernie Sanders, say things like, "Yes, Tom Steyer is a billionaire... [but] it matters what he is doing with that power." Steyer also has endorsements from Climate Center Action Fund, and California Environmental Voters (EnviroVoters). The latter group is also endorsing Porter, as the Times notes.

Could the billionaire thing be a liability in a year when the electorate is feeling particularly angry toward the billionaire class, and when California has a "billionaire tax" on the ballot? Maybe! But we'll have to see.

Related: Steyer Closing In On Hilton In Latest Governor's Race Poll, Becerra On the Rise