This is a very elegant explanation.
TLDR: Mail-in ballots arrive randomly, like a shuffled deck of cards, so when they are counted, the ratio of D to R ballots is consistent, with maybe a slight shift toward R over time, as rural ballots take longer to arrive. This trend held in 45 states.
In 5 States, reporting on mail-in ballots was also consistent, until 2-4am, when the ratio shifted markedly toward D - it would be like shuffling a deck and all the Spades fall to the bottom. Impossible.
The issue as I understand it was that the ballots are NOT processed randomly from across the state. The result you are seeing CAN occur if there is bias from where the votes come from.
NBC (Chuck Todd) and 538 (Nate Silver) has said repeatedly about where the late votes were coming from - primarily from urban areas.
That doesn't exclude the opportunity for fraud but it does provide an explanation that is consistent with the reported data.
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