Getting the 3/5 compromise instead of full representation for slaves still wasn't the cause of the Senate, though. That was itself a separate compromise between those who wanted Congress to be direct representatives of the people, and those who wanted Congress to be representatives of the states. And while it is impossible to entirely disentangle the issue of slavery from the various decisions made during the Constitutional Convention, this was one that primarily was not about slavery and did not break along free/slave state lines; Connecticut (which had already abolished slavery) and New Jersey (where slavery was on its way out) voted in favor of the Senate, while heavy slave states Virginia, South Carolina, and Georgia voted against it. The main issues here were about state sovereignty (because remember, back then people saw themselves as citizens of their states first and of their nation second), and out of a concern that states with fewer people and thus fewer representatives would be at the mercy of bigger states with more representatives, thus the Senate was intended to give all states equal representation in their new government.