I am one of the most pessimistic people I know when it come to the Supreme Court, and even I don't think they would back up Trump trying to nullify election results completely. Bush v Gore is one thing, but going full Putin is another.
You do raise an important issue, and one that can be overlooked when everyone is focused on Congress. Local and state officials decide where the polling locations are! This is a great thing to get involved with during off-years, when there are fewer exciting races to phone bank for. Exactly who decides what can differ by state, so first step is finding out the rules in your state. There may even be positions you can run for yourself, at the county level. Or fuck it, run for state-level positions too!
I no longer have the energy or motivation for small actions, because I'm working many hours, every day, on big federal campaigns. Frankly it is super stressful, and I can't do this role again in 2020 without some serious changes. At least I'm FI, so I can demand the changes I need. That's my off-cycle plan, to get improvements implemented so crunch time goes more smoothly for everyone.