I don't think anyone is arguing that the parties completely switched, but both parties used to be much more ideologically diverse and have both liberal and conservative factions. There was a robust liberal wing of the GOP that was primarily based in the Northeast, along with a large contingent of conservative Democrats mostly from the South.
Now, most Northeastern liberals are Democrats and most Southern conservatives are Republicans.
The Northeastern Republicans were the ones that could be more reasonably described as “far-right,” insofar as anyone can. The Governor in charge of Attica and the population control report was not a liberal.
