The Klan was founded by democrats who not only happened to be Confederate War veterans, but also supported slavery before the war and built a political system to perpetuate it, and when they were thwarted on the filed of battle, built another political system--Jim Crow--to perpetuate their racial hatred.
In every case, it was a certain subset of people--democrats--who had their hand in all these things.
Yes, but I said "Confederate" veteran, not "Civil War veteran". I don't think there were a lot of Southern Republicans at that time. (other than black people)