I’m curious in the history of political parties of the USA. Initially in 1861 Abraham Lincoln was the first President to represent the Republican party which has always been stated as conservative yet, their parties policies seem very liberal in the modern usage of the word.
Also the Democrats had mainly represented the south which today is considered quite conservative. This seems to have switched with the JFK vs Nixon election in 1960, where the Democrats represent the north while the Republicans tend to represent the south. While the Republicans still stay a conservative party and the Democrats still liberal.
My question is, did these two definitions change, and if so how does something like this happen?