The Three-Fifths Compromise gave a disproportionate representation of slave states in the House of Representatives relative to the voters in free states until the American Civil War. In 1793, for example, Southern slave states had 47 members but would have had 33, had seats been assigned based on free populations. In 1812, slave states had 76 instead of the 59 they would have had; in 1833, 98 instead of 73.
As a result, Southern states had disproportionate influence on the presidency, the speakership of the House, and the Supreme Court in the period prior to the Civil War.
For the sake of argument, let's assume the Northern delegates manage to outmaneuver the delegates from the Southern states at the Constitutional Convention and ensure that enslaved African Americans are not counted for the purposes of representation/taxation.
How does this affect American history down the line? Would Jefferson have been elected President? What are the butterflies from this potential decision?