To appropriate an aphorism from Woody Hayes, three things can happen with a Trumpian presidency, and all of them are bad. Which is to say that the 45th POTUS will either be an unmitigated disaster, grossly incompetent, or just not awful.
He has no appreciation of what a democracy is, much less how to govern in one; and is likely to surround himself with a gaggle of people who not only have no interest in preserving our government, but seek to plunder and/or destroy it.
The outcome therefore will depend entirely on (a) how willing the congressional minority is to stand up to him and (b) how willing the congressional majority is to bring him to heel.
For both parties, doing the right thing as described above would be a winning political strategy.
For Democrats, standing up to him would affirm the belief (or hope, depending on your perspective) that they actually are the party of social progress, economic equality and civil justice. In the process, they could reinvigorate their exhausted, tattered base and win the attention, if not the support, of like-minded independents, who now comprise 40%+ of the electorate.
For Republicans, it would reassure nearly 60 million fearful, anxious people that we are not about to be cast back into the era when African-Americans were not allowed to vote and women were treated as chattel. In the process, they could heal the fissures in their ranks caused by Trumpism and reassert the role of the GOP as a responsible conservative entity.
It would be nice if the major parties act out of concern for the well-being of the nation, but that’s not likely to provide the impetus. Rather, the Democrats will do it because nothing motivates a pol to do the right thing like getting killed on E-Day, and the GOP will do it because whatever else may be said about them, they are not stupid.