The biggest thing that Kevin Phillips had going for him in the Emerging Republican Majority was a basic understanding of what areas would be lost as well as gained. I have not read Emerging Democratic Majority so I cannot judge it directly on what it included. However I recall it mentioning Missouri and similar places as being good for Democrats.
I think in general it was too early and it failed to account for more radical shifts in the electorate and the loss of certain places that seemed unthinkable back then, as well as gains in places that seemed unlikely such as Georgia and Texas, which back then were reaching their peak period of Republicanism.
It should be noted also that Phillips himself ran into problems and he never envisioned the loss of the secular suburbs, because he never envisioned the rise of the religious right and the cultural realignment that came along in its wake. Phillips also didn't like the Bush clan at all and didn't foresee Reagan becoming President. Phillips saw the loss of "silk stocking suburbs" and declines in places like the Philly Main Line" but not the wholesale decline of the GOP in places like the suburbs of LA, Chicago and NYC. Finally, Phillips generally doesn't seem to place much value or importance on generational change and that was critical to understanding why changes in the South took so long and thus while even in the 1990's and 2000's, West Virginia and Arkansas were still voting Democratic, which is quite a while later than he had envisioned. He also credited Democratic success in VA solely to the black vote as opposed to generational change among whites and in migration to NOVA.
So in terms of being predictive of the future, "Emerging Republican Majority" likewise had great problems once the changes played out and voters started reacting in kind to those changes and because conservatism evolved in a way that Phillips didn't foresee, a number of his predictions ended up being off like Southern Illinois combining with the Chicago burbs to solidify Illinois for the GOP.
So, he was predicting a map like this:
https://www.270towin.com/maps/4XZAgBasically that every election in the late 20th century would be some sort of variant between 1976 and 1980.
At the moment it sounds like a reasonable hypothesis but its probably incredibly asinine:
Could have the Clinton campaign and presidency been where this potential timeline split off from this one?
Basically, the democrats "made peace" with cutting marginal tax rates and unionization rates by half, the current situation with education and retirement and adopted a peicemeal strategy to health care while looking for issues surrounding civil rights to center on.
Republicans can almost conversely claim a similar argument,.
