What group believed that a strong central government should have more power than the individual states?

The federalist.

Explanation: Those who supported the Constitution and a stronger national republic were known as Federalists. Those who opposed the ratification of the Constitution in favor of small localized government were known as Anti-Federalists. Both the Federalists and the Anti-Federalists were concerned with the preservation of liberty, however, they disagreed over whether or not a strong national government would preserve or eventually destroy the liberty of the American people. Today, it is easy to accept that the prevailing side was right and claim that, had you been alive, you would have certainly supported ratifying the Constitution. However, in order to develop a deeper understanding of the ideological foundations upon which our government is built, it is important to analyze both the Federalist and Ant-Federalist arguments.

The Anti-Federalists were not as organized as the Federalists. They did not share one unified position on the proper form of government. However, they did unite in their objection to the Constitution as it was proposed for ratification in 1787. The Anti-Federalists argued against the expansion of national power. They favored small localized governments with limited national authority as was exercised under the Articles of Confederation. They generally believed a republican government was only possible on the state level and would not work on the national level. Therefore, only a confederacy of the individual states could protect the nation’s liberty and freedom. Another, and perhaps their most well-known concern, was over the lack of a bill of rights. Most Anti-Federalists feared that without a bill of rights, the Constitution would not be able to sufficiently protect the rights of individuals and the states

more information can be found @ https://billofrightsinstitute.org/would-you-have-been-a-federalist-or-an-anti-federalist/

regarding the law, the 15th amendment was specifically designed thinking in the rights of black free men.

even though ratified on february 3, 1870, the promise of the 15th amendment would not be fully applied for a long time.poll taxes and literacy tests would allow southern states disenfranchise african americans. only in 1965 the voting rights for african americans would be actually able to vote in the south.

in 1965, president johnson signed the voting rights act, which aimed to overcome legal barriers that prevented african americans from voting as it was guaranteed by the 15th amendment to the u.s. constitution.