Really a brilliant move by Trump. He's going to lose the popular vote but if his voters go to the polls and Biden's mail their's in, the early polls will have Trump leading. If Trump leads at the end of the night and Biden leads in the morning or it takes days to count the ballots, Trump just declares victory.Because Biden is going to get a much larger share of the mail in vote - according to public polling at least. Thus any shift that makes mail-in votes more likely to get counted benefits him, and any shift making them less likely to be counted benefits Trump.
Per polling data in 538 article linked below (polling data was mid August I think)
Assuming a 50/50 split national vote, that would lead to ~80% of mail in ballots going to Biden.
- 11% of Trump voters said they intend to vote by mail
- 47% of Biden voters said they intend to vote by mail
I was going to vote by mail like I did in the primary but I will vote in person because of this.