(1854) Legislation that organized the territories of Kansas and Nebraska according to the doctrine of popular sovereignty. Introduced by Sen. Stephen A. Douglas to stop the sectional division over slavery, the act was criticized by antislavery groups as a capitulation to proslavery advocates. Groups on both sides rushed to settle Kansas Territory with their adherents, leading to the chaotic Bleeding Kansas period. Passage of the act led to the formation of the Republican Party as a political organization opposed to the expansion of slavery to any U.S. territory