Beginning with this current election, California stopped with paper ballots. You put a scan-tron sheet in a scanner, and there is no paper trail.
No remedy available in that circumstance. The bad guys win.
The Democrats will just have to cheat other Democrats as they are running out of Republicans. It changes nothing on a national level, as long as the mechanism of the Electoral College remains intact and functional.
Eventually that means that other means than elections will determine who rules in California. Mexico provides us with a worked example.