Final answer:
The divisive issue debated at the Constitutional Convention was whether to allow or regulate slavery, leading to a compromise with a 20-year moratorium on laws against slave importation and requirements for returning runaway slaves.
Step-by-step explanation:
The contentious issue that nearly ended the Constitutional Convention without creating a new system of government for the United States was slavery. The delegates from the northern and southern states had a profound disagreement over whether slavery should be regulated or even allowed in the new nation. The southern states, reliant on a slave economy, threatened not to join the Union if slavery was prohibited, while delegates from the North sought to place restrictions on the practice.
To prevent a collapse of the union, a series of compromises were agreed upon. The Constitution included a clause that prevented Congress from passing any legislation to ban the importation of slaves until 1808, effectively a 20-year moratorium. This provision temporarily settled the debate on slavery, but also set the stage for future conflict, as it did not address the fundamental moral and ethical concerns surrounding the institution of slavery. Moreover, the convention stipulated the return of runaway slaves, regardless of whether they had fled to a free state. These concessions reflected the contentious balancing act between the needs for a unified nation and the divergent views on slavery.