How about this hypothesis. Mr. Biden is making his appeal because he needs to win by a decisive margin.
A 52-48 split in popular vote or a 280-260 win in the electoral college means the election is going to be dediced by the Supreme Court. And we know how that insituttion is going to put its 5-4 split decision towards.
No, Mr. Biden needs to put this election by 60-40. Even the Republican domanated Supreme Court will bow to the will of the people--if the will is there.
The future of the USA is in the hands of the 108m voters who did not vote in 2016. I think the Biden team has made a pretty good case for this demographic to make the effort to vote. I would not be surprised if we see a 70-30 split.
Maybe Ms. Martincheck should be out canvassing for D voters rather than writing Medium articles. On election day and after, she would be volunteering to scrutineer the vote counting.