Answer:
Southern Democrats wanted to protect slavery, while Northern Democrats wanted to keep things as they were.
Step-by-step explanation:
At that time, slavery mainly exist on the southern part of United States. Both Northern and Southern Democrats never really work to abolish slavery. Abolishment of slavery generally supported by the Republican party. not the Democrat at that time.
There is one main distinction between northern and southern Democrats. The southern democrats beloved that slavery should be allowed across United States. Northern Democrats were not on board with this because they know that a lot of their supporter base in the north already transitioned to use machines from industrial revolution rather than slaves. The Northern Democrats believed that slavery should stay in the South (keep things as they were). This disagreement lead to the split in 1850s.