The historian Forrest McDonald, describing the split over nullification among proponents of states' rights, wrote, "The doctrine of states' rights, as embraced by most Americans, was not concerned exclusively, or even primarily, with state resistance to federal authority." But by the end of the nullification crisis, many Southerners questioned whether Jacksonian Democrats still represented Southern interests. The historian William J. Cooper Jr. notes, "Numerous Southerners had begun to perceive it Jacksonian Democratic Party as a spear aimed at the South rather than a shield defending the South."