"The parties switched in 1964."
Say what?
If you look at the map there is a lot of truth to that statement.
It didn't happen in one election but by 2012 the states had pretty much switched; Obama won every state that Lincoln won.
Some states have remained consistently GOP (in the west, Kansas for example).
Many states which were and still are very GOP went for Johnson that year.
People conflate an ideological switch with a geographic one, and wildly overstate how much of a clean break there actually was.
Yes, a geographic "switch" happened, but it was accompanied with the death of a generation wedded to big government in a way its successors weren't and Democrats consciously chasing the Northern vote. The "economic left" itself saw a steady shift in its base from South to North. Even then, "Yellow Dog" Democrats were a sizable voter bloc until surprising recently. Obama won those above the age of 80 in some heavily conservative Southern states in 2008 and even 2012...