Several media outlets are reporting success of an effort to gather enough signatures to put a referendum splitting California into three states on its November ballot. If it wins, that is only the first (and perhaps the easiest) of many steps before an actual split can occur.
The proposed states make sense from a SoCal perspective. The coastal area retaining the name "California" is in many ways a world apart - scenic, affluent, retiree-laden, a water-starved near-Eden.
The proposed "Southern California" is an odd amalgam of agricultural, alpine, desert, and south coast. It would vote in Congress with the farm states, and very possibly be Republican.
"Northern California," while geographically compact, contains the leftish Bay Area including Silicon Valley, and the rightish agricultural north valley which has wanted to split off into the state of "Jefferson." Most votes would be in the metro Sacramento-San Francisco-San Jose triangle, so it would be predicted to be Democrat.
Adding four members to the U.S. Senate won't be popular with small states which enjoy their outsize influence. I predict if passed by CA voters, the effort dies in the U.S. Congress or on one of the other hurdles it must cross.
It may never get that far; Cal and SoCal are dependent on water from NorCal which an independent NorCal might want to retain for its own use. And both Cal and SoCal would have to create capitals and associated infrastructure at their own expense, which their voters may choose not to do.