Most of Atcheson’s observations here are very good, but only because the people he calls “centrists” are not central to much–not to the opinions of the nation nor the voting populace, still less to their own party’s voters, and also not to some hypothetical point “between” the parties.
It’s more than a quibble, too, to note that there’s nothing novel in Trump’s bigotry against immigrants. It has been fairly routine Republican drivel since it mostly ceased to be such routine Democratic drivel with the collapse of the “solid Democratic South” over the 1960s leading into the Nixon-McGovern election in '72.
But the goal of Democratic “leadership” is not exactly that Democrats win elections. It is that members of a particular cadre of Democrats win elections. Handing some elections to Republicans with unpopular positions is a small setback to that goal. Handing any election to a candidate–and, by extension, potentially, a movement–that is popular sets those goals back considerably. Moreover, since the funders of both parties are set against the natural and inevitable interests of the populace in relative equality, this tendency gets strongly reinforced by money. And, once various offences are involved, individual politicians and their allies acquire strong personal reasons to retain control.
What all this means is that losing to Donald Trump again is again not going to change the minds of the Democratic Party, whatever it may or may not do for Democratic voters. Whatever change happens within or without the Democrats, it cannot be a “Vote Blue” wave.