Answer: the Free-Soil party commanded that slavery not be extended to the territories and Kansas-Nebraska Act allowed settlers in newly organized territories north of the Missouri border to resolve the slavery issue for themselves.
Explanation:
It was a form of winning the Southern legislators support, in a matter deeply related to them. By using the excuse of "popular sovereignty", Senator Douglas enabled a bill that allowed voters could decide if they would allow the implementation of slavery in their territories or not.
