The Republican base notoriously votes against its own economic interests time and again in favor of social/moral alignment with “traditional values” — in other words with the dominance hierarchy. That’s not just blue-collar white guys. 47% of white women voted for Trump — for the same reasons — to maintain their place in the dominance hierarchy. Of course, the die-hard base isn’t going to vote for Biden, but Trump’s presidency has been enough of a cluster that a lot of more moderate people don’t want to see him back, although they might choose him again if it’s a choice between him and someone like Bernie, who aims to completely shake up the dominance hierarchy. In a time of upheaval, in particular, people want someone who represents stability.
Trump’s mishandling of the pandemic is further alienating even more people. I’m not saying it’s a given that Trump will lose, but I do think that of the D candidates, Biden is the only one who has a real chance to unseat him.