Most dumbocrats never voted by mail before and will make mistakes that will invalidate their ballots.
Naked ballots, envelopes without signature, ballots sent in late, etc. And the post office fails to deliver about 3% of the mail. They will need a lot of fraud to win.
Mail in or absentee are not popular with Democrats because they presume you can read and write...though the DNC most likely has a ‘work-around’ for that.
I took election day and following two days off for vacation. I’ll get up early and get to the voting venue to be at the head of the line.