After the Civil War, Lincoln supported a mild Reconstruction of the South. Which group favored a much harsher reconstruction plan in the South? A. Radical Republicans B. Moderate Republicans C. Democrats D. Ku Klux Klan

A is the correct answer.

Radical Republicans in the House and Senate opposed Lincoln's leniency towards the South.

They believed, possibly correctly, that the South had common treason and deserved to be fully punished and forced to make reparations for the damage it had done to the Union, both politically and financially.