How did african americans strengthen the republican party in the south

African-Americans helped to strengthen the Republican Party by voting in Republican legislatures. African-Americans in the South were strongly Republican during the era of Reconstruction (which took place right after the Civil War) due to the stance of Lincoln and other Republicans who abolished slavery. Along with this, the Republican party was the political faction that helped to get the 14th amendment passed, which gave African-Americans citizenship.

Word of mouth.