As I’ve noted before, Trump’s outrageous tweets aren’t simply intended to blow off steam and endear him to his base; they let him dictate the terms of the debate on any given day, and they are designed to provoke a PC overreaction that can be used to persuade swing voters that, of two flawed candidates, he is the one who is most on their side. Judged on those terms, the tweets are frequently successful.
So how should the Democrats’ 2020 nominee respond? Mostly, by ignoring the tweets, staying on message, and remembering that base mobilization is not going to be a problem; the objective is to win over the undecided, and overreactions do not help.
It worked in 2018. There is no reason to believe it can’t work again, provided the nominee has the requisite self-discipline.