Aren’t there pollwatchers from both parties who would be privy to the preliminary results? And wouldn’t the Democrat pollwatchers in the Republican precinct report those preliminary results back to headquarters?
Poll watchers must have worked well in the 2020 election in Pennsylvania. When Philadelphia had reported its vote before large parts of Western Pennsylvania I first thought that Trump had a chance to win.
On the other hand, in some of our big blue cities there are precincts in heavily Dem areas, where no Republican is willing to go to be a poll watcher or even an election judge. Every precinct must have a head judge and an assistant from each party, however, if no Republican chooses to go to certain precinct, then Democrats can step in and“help“.
One of the old-fashioned ways of cheating was to vote for people who never showed up in such a precinct. With mail in balloting, etc. who knows now how many ways there are to cheat.