I'll take a bit of a risk here:
Party polarization on social issues declines, but polarization by industry between manufacturers (GOP) and raw material producers/exporters (Dem) increases. Deindustrialization spreads through New England and then to the NYC metro area, driving them toward a less religious and more populist GOP. Tariffs cause a split in both the environmentalist and energy industry vote. The GOP positions itself as the party for retirees and moderates enough on climate change to lock down Florida. Meanwhile, big Dem gains in the Deep South and Plains states lead to a growing religious left bloc that is starting to make NorCal and the Pacific NW states uncomfortable. Dems finally take the Mormon vote after a long period of flirtation with 3rd parties in Utah and Idaho.
Thoughts?