Answer: The act spurred more people to join the movement, making it stronger.
Step-by-step explanation:
Up until the Kansas - Nebraska Act the western territories of the United States did not have a set policy on slavery and Northern abolitionists were fine this because they hoped to abolish slavery there and then in future, have the necessary influence to abolish it nationwide.
The act therefore galvanised support for the movement and made it stronger as abolitionists were worried that if slavery should spread into the west, it would make it that much harder to abolish.