That's not how voting works. There are reps from both parties present at each precinct, there is an inspector of elections for each jurisdiction, a director of elections and voter registration appointed by the governor for each county, and of course the state board of elections at the top. If there's mistakes, and they do happen, it's pretty much always a case of incompetence or techinal issues. Actual cheating is very rare and very difficult to pull off without being caught. North Carolina had a recent cheating scandal involving absentee ballots being filled out by some group of weirdos. People went to jail. Felony stuff. Voter fraud is big deal. There are, in fact, a lot of intelligent people from poll workers to strategists to lawyers from each party and each campaign keeping track of what's going on. Feeding ballots is nonsense, unless you think your home team is too incompetent to count and make evidence-based legal challenges like big boys and girls. Rah Rah Rah go team!