Here is a summary of the switchover from democrat to republican.
Sorry blondie, but Wikipedia is fake news when it comes to political articles. Leftists activists are all over it, using it as propaganda.
So it is possible that some southern Democrats in past supported and were backed by the KKK.
"possible"? Not every democrat was a KKK member but every KKK member was a democrat.
The notion that they switched is baloney. The democrats voted against civil rights until the damn burst and then they switched to using the welfare state for enslavement.
The notion that they switched comes from the democrats original use of the accusation of racism against their political opponents, it worked so well they have been doing it ever since. They don't care what race, they don't care about the people, they just enjoy the tactic because up until now it was a winner ... but they've over played it and Trump doesn't follow the old rulebook anymore.
Fun fact: the nazi party based a lot of their ideas on the democrats platform ... but they decided they needed to tone down the level of racism. Yeah, when the nazis think you're too extreme ...