Gazillionaire investor and progressive-minded mega-donor Tom Steyer has endorsed Democratic California Sen. Dianne Feinstein’s primary challenger, Kevin de León, the Los Angeles Times reports. Here’s how Steyer framed his choice:

“I think he’s the kind of young progressive that reflects California and would be a very strong advocate for our state nationally,” Steyer said in an interview on Tuesday, pointing to De León’s efforts on issues such as immigration, climate change and gun control while he was the state Senate leader. “I know him well and he’s a friend. We share a lot of values.” Steyer, who flirted with running for Senate, did not criticize Feinstein as he has in the past. “Sen. Feinstein has been an outstanding public servant who has dedicated the bulk of her adult life to the service of our state and the country,” he said. “These are two strong, very good Democrats. I just believe Kevin is the true progressive and he reflects something we need representing California going forward. I have nothing bad to say about Dianne Feinstein. I have a lot of good to say about Kevin de León.”

Feinstein has proverbially drawn the proverbial ire of Democratic progressives nationwide for her relative deference to Donald Trump, which is particularly striking given California’s liberal electorate. She voted to confirm 11 of POTUS’s 22 Cabinet nominees—her fellow Golden State senator, Kamala Harris, voted “yes” on only four of them—and told a San Francisco crowd in August 2017 that she still believed Trump “can be a good president.” (“The jury’s still out!” —Dianne Feinstein amid a post-apocalyptic nuclear hellscape in 2024.) De León has taken advantage of the opening, winning enough votes at the state’s 2018 Democratic convention to deny Feinstein her party’s official endorsement and, last week, earning the support of California’s AFL-CIO affiliate. Now he has Steyer too.

On the other hand, Feinstein still has a 25-point lead in the polls and a major fundraising advantage; Steyer wouldn’t tell the L.A. Times whether he plans to fund an independent group to support de León, which is the obvious way he could really help the challenger’s chances. Still, because California has a single open Senate “jungle primary” in which the top two candidates move on to a runoff in the general election, and because Republicans haven’t fielded a serious candidate of their own, de León almost certainly will have until November to persuade his state’s voters that he’s the right guy. In this, he will have the support not just of antsy leftists elsewhere in the country, but also mainstream journalists such as myself who will write disproportionately about his race simply because the potential “battle for the soul of the Democratic Party” narrative is so compelling. It’s going to be fun!