I see some flaws in the detailed data. For instance, Trump only polls 4% better than Biden among southern voters? The last IBD/TIPP regular poll had the race withing the margin of error, and the 5 point jump for Biden in their first tracking poll is puzzling. Also can’t find their sample size by party.
The internals were 321 Democrats, 298 Republicans (7 percent Democrat oversample) and 234 Independents (a good number of these would likely vote for Bernie Sanders or Jill Stein).
I have only come across 1 Biden voter here in South Carolina that I know.