Three days before the election, The Postmaster General, under orders from POTUS, secretly changes the postmarking machinery and hand stamps in all Post Offices.
The new postmark is similar to the previous ones, but has identifying marks which make counterfeit postmarks obvious to all. All ballots with counterfeit postmarks are invalidated and seized for forensic analysis. Anyone who possesses or attempts to pass counterfeit ballots is immediately arrested for ballot fraud.
A week after the election, it is found that the Trump landside has held. No "late" or "found" ballots exist, at least not valid ones. Several thousand people are waiting in jail for trial and sentencing for attempted ballot fraud.
That is genius! You win the internet today....
nov. 4 postmark change idea bookmark