A good demagogue never lets something as insignificant as facts get in the way of their spiel and narrative.
Indeed, but what I find infuriating is that there are significant numbers of people who will continue to believe the narrative. I can point to people who now believe that mail-in ballots are fraught with fraud, and who will defend that belief to the death simply because the demagogue said it.
My state is a Republican stronghold. We've voted almost exclusively by mail for the past several election cycles. I can't remember the last time I actually visited a polling place. In the last general elected we had one instance of voter fraud. Utah law allows for members of the Mormon church serving full-time missions outside the state to vote as absentees in Utah elections. (The law is sensibly worded to extend this to all Utah residents similarly situated, without regard to religion, but its intent is clear.) However, the ballot must be mailed to them directly. Not all such residents made the appropriate arrangements, so they instructed their parents in Utah to complete the ballot on their behalf. This is illegal, and it was detected.
Prior to the last primary election, a computer glitch caused a small number of ballots to be mailed to minors. Utah law allows 17-year-olds to preregister to vote if they will have turned 18 prior to the general election for which the registration is to be considered valid. The computer checked the date of the general election, but failed to check the date of the primary election. The clerk's office caught the error and simply invalidated the ballots by a few keystrokes in the computer.
I realize this degree of electoral fidelity is common in more well-developed countries, but it is an example of what has been achieved in some parts of the U.S. There is simply no truth to the claim that a U.S. election conducted by mail would be more susceptible to fraud than any other method, and Republicans know this.