Why the Parties Switched

I've often wondered how it came to be that the party of Lincoln became the party of Trump, and the party of segregation became the party of the Voting Rights Act.

UC Davis History professor Erich Rauchway wrote a nice little blog post over a decade ago detailing how it basically happened between 1866-1936.  He ends with this nugget:
Now, one can get cleverer and point out that although the rhetoric and to a degree the policies of the parties do switch places, their core supporters don’t—which is to say, the Republicans remain, throughout, the party of bigger businesses; it’s just that in the earlier era bigger businesses want bigger government [federal aid for the transcontinental railroad, for the state university system, for the settlement of the West by homesteaders; for a national currency and a protective tariff] and in the later era they don’t [banking, securities, and currency regulation; relief for the unemployed and pensions for the elderly; wilderness conservation; improvements to roads and electric infrastructure; support for unionization; and much else].