By itself, however, the three-fifths compromise for representation was not enough. Facing deadlock at the Convention, Gouverneur Morris (representing Pennsylvania) moved on July 12 to add a ...

there was also an indication of northern reluctance to see the extension of southern political advantage by inflated representation (tied to the three-fifths compromise of the federal Constitution).

This desire led to a compromise known as the “three-fifths compromise,” where each enslaved person would be counted as three-fifths of a person for purposes of representation in Congress.