Final answer:
The Three-Fifths Compromise allowed the South to count three-fifths of slaves for representation in Congress and the Electoral College, increasing their political power but also deepening national divisions over slavery.
Step-by-step explanation:
The Three-Fifths Compromise significantly affected political power in the South by influencing the representation in the House of Representatives. This compromise, reached during the Philadelphia Convention of 1787, allowed Southern states to count three-fifths of their enslaved population when apportioning Congressional seats, thereby increasing their political influence in the federal government. It conceded that a slave would be counted as three-fifths of a person for the purpose of both determining representation and taxation.
This increase in representation elevated the Southern states' powers within the House and the Electoral College. It also granted them more influence over federal policy, including policies about slavery. However, this compromise further entrenched the institution of slavery in the political system of the United States and exacerbated tensions between Northern and Southern states.