Trump's support has remained steady almost no matter what he does. So if he were reelected, we can't look to the Party of Trump (PoT)* to do us much good in breaking down the tribal barriers that now pervade our national political life. In fact it seems likely that we could count on a further deterioration, to the point of ruin. So obviously, the moderate course is to rely on the Democrats.
Will Biden and Harris be able to reach out? I'm not optimistic. They'll be too busy with trying to undo the regressive trends that Trump and his sycophants have tried to implant in so many areas (literally ALL areas). They will also working to establish new progressive models, as voters clearly expect, to deal in more creative ways with matters that now seem higher-profile than before -- racism, national health care, income distribution, and climate change, to name a few. They will be doing this not only against the pushback from Republicans who survive the election, but possibly also from different factions within their own party. These jobs will take years; a full Presidential term or even two. And if they should craft some semblance of bipartisan consensus on measures addressing one or two issues, the only barriers that get broken down will be those among a handful of politicians.
This is all good and necessary work, but not enough to keep 2024, or 2028, from looking just like 2016, when we will be looking again at a very narrowly decided election, and we'll be off again on the next Trump disciple's rush to take the country back to the 1950s or earlier.
Could it be that Biden and Harris need to go much further? Trump's base is real. Certainly it includes malevolent and self-interested politicians who lead them down garden paths, and it includes a small tranche of people who really are "deplorables," not the "fine people" Trump so infamously declared neo-Nazis to be. Democrats should keep in mind that until the mid-1960s, those same deplorables were voting Democratic. But that's the fringe. I believe that mostly the 40%, or 45%, whatever, are just regular Americans. They too have to pay the bills, deal with their health, educate their kids. They vote, they have issues they legitimately expect their government to help deal with, and - useful to keep in mind - issues where they believe the government ought NOT to get involved. If they are on average more white, more male, older, less educated, or live in less densely populated areas than those on the other side of the political divide, they are still as American as apple pie and violence.
As a nation, what shall we "do with" this large contingent? If we're going to get past the current state of intense polarization, they are the people to whom Joe and Kamala will need to reach out. Frankly, in the current environment of mutual suspicion and hostility, I don't see how the more extreme proposals of the left get us there. History suggests a President may be able to bring one major change to fruition during a new term. On the other hand, many commentators are seeing hope that the current juxtaposition of several churning crises (black lives matter, climate change, attacks on our constitution and voting procedures, coronavirus) can produce another era of sea change a la FDR. I don't see Joe Biden in that mold.
*There is a terrible punster behind the curtain at Morning Fog who suggests that probably the PoT would rather just sit back and call the kettle black. Or maybe destroy the kettle.