A given election district (precinct, city, county, etc.) has x voters on the rolls. X — especially in urban districts — is heavily-padded with the unpurged dead and otherwise departed, and with folks who have registered but never bother to vote. The names of everyone in x are in a computer database.
By the end of election day, a portion of x who we’ll call y1 have requested and been sent absentee ballots (and probably have mailed them in) — but in theory, everyone has been sent a ballot for mail-in voting, whether requested or not. Another portion of x (we’ll call them y2) have cast ballots at the polls.
The names of everyone in both y1 and y2 are in a computer database by the end of election day.
NOW, WITHIN A FEW BUSY HOURS after the polls have closed and the number of extra votes needed has become apparent — say, by 3:00AM to 4:30AM the next day — y1 can be added to y2 and the total subtracted from x, yielding z: the number of fraudulent ballots that can be tossed into the pot, all marked for the fraudster’s candidate, without exceeding the theoretical (or plausible) maximum for the district.
Every one of these fraudulent ballots can e ...