I say find the boxes, dump the contents and burn them.
I wonder what would happen if you just poured some water in them. I wonder how often they pick up the ballots. I think it would only take a couple hours to ruin a whole bunch,even if they only have those little slots that you can’t get much through you could get a tube and hook it to a plastic bottle and squirt a lot of water into a box.
I imagine liberals are probably going to have cameras on them this year so you’d have to be pretty careful.