According to three unnamed sources, CNN is reporting that state Senate President Kevin de León "intends" to launch an intra-party challenge to California Sen. Dianne Feinstein and will make an announcement "soon." De León, a Democrat who represents a seat in the Los Angeles area and faces term limits next year, had previously refused to rule out a bid and harshly criticized Feinstein for counseling "patience" toward Donald Trump, so it wouldn't be any sort of surprise to see him jump in, though he has yet to confirm his plans publicly.

Billionaire activist Tom Steyer has also been considering a run for Senate, and he may be more interested than he'd previously appeared to be. Just the other day, Steyer (who's also talked about running for governor and even president) merely said he was "considering all options," but now, according to another nameless source, Steyer is "very much looking at the Senate seat."

It's very hard to game out what a three-way race might look like between Feinstein, de León, and Steyer, and to make things more complex, a second rich guy, Joseph Sanberg, is also weighing a bid. But one problem any Democratic insurgent would face, even if they can make it past the top-two primary for a one-on-one matchup with Feinstein, is the fact that Republican voters would likely side with the incumbent over a more liberal challenger in the general election. It'll be a long while before we see polling that can meaningfully address this issue, though.