Unfortunately, most of what I have read indicates that Biden is a proud guy, and I think he'll talk himself into believing he can win. Stephen King said "We lie most effectively when we lie to ourselves", and I think that's what will happen. Biden should step down, but the people around him aren't going to tell him that.
Can you paint a scenario in which, if Biden stood down, the Democrats could find, nominate and successfully sell another candidate in the 4 months left before the election?
Granted, the party has a process in place for how it could be done (finding a replacement). Under the existing rule, Democratic National Committee Chair Jamie Harrison would name a new nominee, in consultation with Senate Majority Leader Chuck Schumer, D-N.Y., House Minority Leader Hakeem Jeffries, D-N.Y., and Democratic Governors Association Chair Tim Walz of Minnesota. Their choice would be presented to DNC members — a group of party leaders much smaller and more elite than the delegates to the convention — for ratification or rejection.
And this group of elites would present their nominee to the committed delegates Biden has already won, and naturally they will all think, "Oh, how clever of our overlords -- how could we have been so stupid?" (Out of interest, Biden has won nearly 4,000 delegates, Trump 2,265.)
And then there's selling this new person -- with no record to run on -- as being so much better than Trump, who has at least served a term in the White House.
In my view, Biden's resignation would hand the election to the fascist. In a landslide.