i'm thinking that from the boomers onward this has been the case in which they predominantly lean left, and that comes from school and peer group but changes as they age;

The Journal article was written by pollster and ex-Clinton advisor Mark Penn and ex-NYC politician Andrew Stein. The piece itself is behind a paywall, but ZeroHedge relates its thesis, writing:

A sizable proportion of young Americans lean heavily to the left, often with limited understanding of history, moral grounding, or the foundations of Western civilization. Whether it’s the result of leftist indoctrination on college campuses or the intellectual decay sparked by endless hours on social media, the effect is apparent: radicalism is here to stay.

Rights and Lefts Mixed Up?

Before proceeding, a seeming contradiction must be addressed. Much has been said in recent years about how Gen Z is “has taken a turn toward conservatism.” This appears to contradict the useful (leftist) idiot thesis. The answer, however, is that the picture is nuanced.

First, there’s a huge sex divide apparent, with young women turning hard left and young men tacking somewhat right. The latter is especially true among young white men, the most conservative Gen Z segment.

Yet there’s also a misunderstanding about “conservatism” itself. Its only consistent definition relates to a desire to “conserve” the status quo. And today’s cultural/political status quo is decidedly more left-wing than that of a generation ago. Thus, while some young people are on the political spectrum’s right side, that spectrum itself has shifted left of where it once was.........more.........