How so? I've volunteered to help run elections in two states in the US, and they both used optical-scan paper ballots. In both jurisdictions, the voter is the o

How so? I've volunteered to help run elections in two states in the US, and they both used optical-scan paper ballots. In both jurisdictions, the voter is the one who feeds their ballot into the scanner machine ("ballot box") to be counted. The machine makes a digital copy of each ballot and stores it in local memory. At the end of the night, we then report the number of ballots in the box and compare it to the number of ballots we issued out and the number of people who checked in at the registration desk. We call these numbers in, and the precinct chief hand-delivers the paper ballots, digital scans, and seal records to the county for legal and archival purposes. In order to manipulate this, you would need the entire polling place staff to be in on the conspiracy, and they would need to cook up numbers and ballots that all match. All to mess with an election at a precinct with no more than ~1500 registered voters. Where those voters are likely of the same political persuasion as the poll workers themselves. High cost, low reward.