This is coming from a Californian: I am skeptical, purely in terms of political advantage, that it is a good idea for the Democrats to run a California politician for the presidential slot in 2028 unless they are absolutely extraordinary. Two major potential Democratic 2028 nominees, Gavin Newsom and Kamala Harris, are both out of California.
California is going to vote for the Democratic candidate regardless of who it is. If the Democrats nominate a dead orangutan, California will vote for it. It's like the Republicans nominating the governor of Utah. (Actually, my understanding is that the current governor of Utah is kind of a decent guy, has been one of the people tamping down on divisiveness, but still, Republicans just aren't getting a geographic benefit out of nominating him).
I'd be more inclined to think that someone like Gretchen Whitmer, the governor of Michigan, would do well in the general election. She's managed to win over voters in the Midwest, which have been swing states in recent elections, which is what the Democrats might actually not win in 2028. Biden was out of Pennsylvania.
IIRC from past reading, predictions are that 2028 will see some states further in the southeast might becoming swing states; it's not as if the set of swing states are fixed. But I am confident that California will not be among the 2028 swing states short of a cataclysmic political upheaval in the next three years.
All that, of course, is entirely disregarding their policies.