Reacting 2: The Constitution, the Articles, and Federalism: Crash Course US History

The Northwest Territory was the first step toward using the government to end slavery.
The 3/5ths Clause was to prevent the South from having unearned representatives who could have a supermajority in Congress allowing slavery to become more intrenched.
Once the Constitution was ratified, there is no way out, unless the government violates the Constitution.