After the votes are tallied and it's said to be certiefied and "officially" over and counted from whatever government entity that community would check their results against the "official" ones.
I know that exit polls are designed to get an idea of what's going to happen but I'd love to see a scenario where a community, ahead of time, put this type of security in place to test and see if the people counting the votes / people creating these machines / any outside forces had a hand in tainting the election.
It wouldn't matter what party you voted for, it wouldn't matter who the candidates are, and hopefully people no matter their political beliefs would all agree that finding out if their vote truly matters or not is more important than any sort of partisan bickering.
It's nice to daydream though, is it not?
I was going to suggest that such people could just film themselves voting. But then I realized that with today's technology that's easily faked.
I'm not sure I've ever seen a video stream of ballot persons actually counting paper, so it may not be monitored publically
Russia successfully infiltrated the NRA, I'd imagine local ballot groups wouldn't be much harder for a foreign adversary to do
Exit polls give you a pretty good idea, within a margin of error, of who is winning. If somebody is winning by a large margin and you want to change that by hacking voting machines, it is very likely to be detected by the exit polls.
In a real dispute exit polls are worthless.
The problem is that the paper ballots may never be hand counted if the margin between the candidates given by the electronic vote counting machine is far enough apart.
Of course, whoever hacks a vote counting machine can give any vote count they want, so they can set the margin however wide they want.
The only way to really be sure of the totals is to do hand counts of paper ballots, with representatives of each party participating or at least observing the entire count.
Machines should never be trusted.