Slavery could not "expand" to new territories. You could not grow cotton in any of the territories, and that was the absolute primary usage of slaves in that era.
The claim that it would "expand" was a lie meant to scare people. What they were really afraid would "expand" was the possibility of states coming into the Union that would be allied with the Southern states, and therefore help them repeal the corrupt and unfair laws that had the Southern states paying 72% of all the taxes.
The "expansion" claim was just a political lie and people are still swallowing it today.
Pure unadultrated BS.
You simply are detached from the reality of the day. You haven’t read any of the pro-slave literature if you believe this.
Now, I’m done with your Confederate blather. The DemoKKKrats founded the Confederacy. They are the enemy, they are the pro-abort people and slavery WAS the abortion debate of the day. They are, and remain the party of death. If you are supporting the Confederacy, you are definitely supporting the evil party.