The problem with mail-in ballots is that they're more likely to be voided, so you could have more people who intended to vote for Biden.
Anyway, the annoying betting market update:
7:55 am Biden at 61c, Trump at 44c.
3:45 pm Biden at 70 c, Trump at 39c.
4:59 pm Biden at 68c, Trump at 43c.
7:13 pm Biden 32c, Trump 78c.
7:17 pm Biden at 18c, Trump at 78c.
7:35 pm Biden at 34, Trump at 77c.
7:41 pm Biden 33c, Trump 69c.
7:51 pm Biden 36c, Trump 67c.
7:57 pm Biden 42c, Trump 66c.
7:58 pm Biden 34c, Trump 65c.
The market's obviously very volatile. Lots of panic. The numbers for Trump winning WI, MI, and PA have all come down to about 60c. Biden's way ahead in AZ and in the low 70s for NV (which was given to Trump briefly).