I agree that someone should look into this and see if it is indeed an issue. I don't know if anyone has checked on it (but if you can provide a link to someone who has, that would be interesting to read). ... That said, just because a possibility exists does not mean it is a significant form of evidence. Such a claim needs investigating, and if no one has done that, a reasonable person would not call it legitimate evidence (or use it, especially in presidential discourse); that voting issue is a theoretical possibility, but so are many, many other ideas that have not been proven. The burden of proof is on the person who uses the claim, not on everyone else to figure out how it could be true.