What ideology strongly supported the institution of slavery in the South during the 19th century?

The correct choice is the ideology that strongly supported the institution of slavery in the South during the 19th century. Pro-slavery ideology defended slavery on various grounds, including economic, social, and racial arguments. Proponents believed that slavery was essential for the agricultural economy of the South, particularly for the production of cash crops like cotton and tobacco. They argued that the labor provided by enslaved people was necessary for the economic prosperity of the region.

Furthermore, pro-slavery advocates often asserted that slavery was a positive good, suggesting it was beneficial for both the enslaved individuals, who they claimed were better off under such a system, and for Southern society, which they believed relied on the hierarchical social structure that slavery maintained. This ideology was deeply rooted in the South's cultural identity and political establishments, influencing legal, social, and economic policies of the time.

Other ideologies, such as abolitionism, opposed slavery and sought to end the practice, while federalism and republicanism represented different political concepts and governance structures that did not inherently support the institution of slavery. Therefore, the distinct and active promotion of slavery through the pro-slavery ideology explains its central role in Southern society during that period.