The Ku Klux Klan, intimidating and terrorizing black and white Republicans since the 19th Century.
The KKK went after everyone who didn’t tow the Democrat Party line. They were founded by the Democrats as their political action wing.
Well, that’s one viewpoint...... But, from my researches, the “Klan” arose in response to the predations of norther “carpetbaggers” following the end of our 1st Civil War. (First is intentional, BTW) That it, like many other worthwhile populist movements, morphed into something else in its later iterations is, from the perspective of history, predictable. >PS