1. Give Republican badges to Democrat poll watchers. Now what seems like a fair polling place with representatives of both parties is really stacked with just Democrats.
2. If someone shows up to vote and their name is not on the list or has already been signed off, then the person who runs the polling places bullies the pollworker claiming it is some sort of error and let the person vote anyway. Thus the same person can vote at multiple locations.
Acquire hundreds of red MAGA stickers and place on rat cars! Watch the burn! :-)