Complex sentence: Second, political power in the Southern states should pass from the planter class to his beloved "plebians", especially since many African-Americans were still economically bound to their former masters, and might vote at their direction.
Split into simpler sentences: Second, political power in the Southern states should pass from the planter class to his beloved "plebians". Johnson feared that the freedmen, many of whom were still economically bound to their former masters, might vote at their direction.