That's not the story the whistleblower tells. The plan, for example, is to reject entire batches of ballots if a single ballot doesn't pass USPS's criteria.
Sure, that sounds scary. But the USPS’s criteria are all about the barcode, the envelope, etc. If the state cannot print envelopes that the USPS’s sorting machine can read then it will reject them. And if the very first one in a carton of mail is wrong, what are the odds any of the rest will be right?
