Here's actual data from Wisconsin. https://elections.wi.gov/index.php/node/7181. Wisconsin doesn't register voters by party and that information is not known. 785,553 absentee ballots have been cast so far (approx 2.7 M votes total in the 2016 election). Early voting doesn't start until October 20.
I'm not sure how you can read much into that, except to say that there were a shit ton of absentee ballots received in Dane and Milwaukee counties, which are the two most liberal counties (Madison and Milwaukee). How that translates into final vote, who knows. Maybe it's just that people in those areas got more absentee ballots due to Covid?
And anecdotally, I have family in Wisconsin, and the sense I get is that they are still royally pissed at the games the GOP played with the vote in the primary this summer, and also with trying to throw out votes a few weeks ago. At the least, I'm sure there's a lot of enthusiasm on the dem side.