The two significant points about how the Ku Klux Klan gained power and influence in the South are:
A. It was a group of white Democrats who wanted to regain control of the government
D. The group influenced the voting behaviors of citizens through threats.
These options highlight the Klan's political motivations and intimidation tactics, which were key in their efforts to suppress African American civil rights and maintain white supremacy in the post-Civil War South.