What side in the slavery debate lost territory because of the Kansas-Nebraska Act of 1854?

The Kansas-Nebraska Act of 1854 primarily impacted the pro-slavery side, as it allowed for the possibility of slavery's expansion into territories that were previously designated as free under the Missouri Compromise. The act led to violent conflicts known as "Bleeding Kansas" as pro-slavery and anti-slavery factions clashed over the issue. Ultimately, the increased tension and violence shifted political power and public sentiment against the pro-slavery stance, contributing to its territorial losses in the long run.