^I think the long-term consequences at the presidential level would be far more disastrous for the GOP, with states like TX, MS and GA becoming battlegrounds. If the Democrats play their cards right, they'll be able to lock the GOP out of the White House for maybe another 20 years.
Nah, I doubt it. When Trump loses, the unanimous backlash against him will be a sight to behold. The GOP will recover quickly because their voters are idiots with short memories. You talk about 1964; look what happened four years later.
That's not that good a comparison to make, considering there was a fairly strong third party challenge (Wallace) and Nixon won with only 42% nationally.