Who did republicans gain control of southern state governments during reconstruction?

Republicans gained control of southern state governments during Reconstruction primarily through the support of newly enfranchised African American voters and the assistance of Northern abolitionists and carpetbaggers. The federal government also played a crucial role by implementing military Reconstruction Acts, which divided the South into military districts and required states to create new constitutions guaranteeing voting rights for Black men. This political shift was met with resistance from Southern Democrats, leading to significant social and political tensions in the region.