Each of our two major parties have, in the last decade, been taken over by forces always present but never dominant until now. Along the way each lost support of former stalwarts. One wonders at the timing.
The Republicans were taken over by the nationalists and populists. Along the way they shed all of the globalists, at least some of the libertarians, and corporate leadership.
The Democrats were taken over by the grievance groups and what passes for the hard left in this country. Along the way they shed the evangelicals and most of the labor movement (except government unions).
Wall Street mostly changed sides, Main Street didn't. Much of the upper middle class - a former GOP core group - has morphed into Kotkin's "clerisy" and switched to the D side.
Along the way, we sorted ourselves out so that Republicans mostly live in low-density places, and Democrats mostly live in high-density places. The battle lines are drawn between the inner and outer suburbs.
Bob Dylan was channeling Nostradamus when he sang, "The times, they are a-changin'."