There's only been one poll so far of the California 2024 Senate race. A poll sponsored by Katie Porter showing her beating Schiff 37% to 26%. Schiff for his part has a massive war chest already from the previous cycle, so he's got a large fundraising lead.
Barbara Lee is also officially running in the race.
Ro Khanna is considering running for the seat as well.
California operates an open primary system where the top two vote getters regardless of party advance to the general election. So it is entirely possible that the Senate race will be two Democrats facing off against each other. That is what happened in 2016, and 2018.
Generally only a third of the electorate votes Republican in California in the primary, so even a crowded Democratic field could get the top two slots. For example, Democrat Kevin de León got the second slot in 2018 with only 12% of the vote.
If all three Progressives do in fact run I think I'd give the edge to Schiff at this stage. But it will be an interesting race.
They are all strong candidates.