Final answer:
The Constitutional Convention's key debate was on slavery, focusing on how slaves would be counted for representation and taxation, and the future of the institution under the new constitution.
Step-by-step explanation:
The main subject of debate among delegates to the Constitutional Convention was the institution of slavery. This contentious issue highlighted sectional divisions, as delegates from the Southern states, where slavery was widespread and integral to their economies, clashed with those from the Northern states, where there was a stronger anti-slavery sentiment. The debates also centered on whether slaves should count toward a state's population for purposes of representation and taxation, and to what extent the new constitution should acknowledge or limit the practice of slavery.
Other prominent topics of debate were the distribution of power between the state and federal governments, the representation of states in Congress, and methods for electing the President. The convention ultimately resulted in the creation of the United States Constitution, which introduced a stronger federal government structure than that provided under the Articles of Confederation, while also making significant compromises regarding the issue of slavery.