If I was going to fraud an election, this is how I would do it

I would have an algorithm connected to a database of all registered voters in my state. As each ballot is counted it would check off that registered voter's eligibility to vote and mark them down as "voted".

After doing a large bulk of the available ballots, I'd stop counting, and make sure no one was overseeing my next step. Eventually I'd have so many of the eligible and registered voters marked off as "voted" I could just start filling out ballots for voters that hadn't been marked off yet...at the very end of course. And in case these registered voters did end up voting and their votes were later found, I'd have the algorithm "correct" the vote tally to showcase that voters correct ballot. That's just how I'd do it.