Paying off witnesses will go a long way towards crushing any credibility of their stories. Their testimony will be needed for the legal record. Besides it is a criminal offense to witness tamper. Its ok to pay for a tip, but that tip does not get testified to by the informant. Its money for testimony that is illegal.
All you need to do is to find one person who counted illegal ballots. Arrest that person. Then, tell them they will get full immunity if they cooperate. Otherwise, prison sentence. I’ll be there will be many hundreds if not thousands of these people and some bragging about how they cheated.