How did african americans strengthen the republican party in the south?

If this in the post-civil war era then it is because the Republicans were the anti-slavery party at the time and push for the freedom and the equality of freed-slaves. However they didnt do it because they through the practice was morally apprehensive they just wanted to hurt the South as much as possible in order to punish them for splitting from the Union.

Ithink the answer is a.