1850s
In the 1850s, in the runup to the Civil War, Northern Democrats led by Senator Lewis Cass of Michigan and Stephen A. Douglas of Illinois promoted popular sovereignty as a middle position on the slavery issue. It said that actual residents of territories should be able to decide by voting whether or not slavery would be allowed in the territory. The federal government did not have to make the decision, and by appealing to democracy Cass and Douglas hoped they could finesse the question of support for or opposition to slavery. Douglas applied popular sovereignty to Kansas in the Kansas Nebraska Act which passed Congress in 1854. The Act had two unexpected results. By dropping the Missouri Compromise of 1820 (which said slavery would never be allowed in Kansas), it was a major boost for the expansion of slavery. Overnight outrage united anti-slavery forces across the North into an "anti-Nebraska" movement that soon was institutionalized as the Republican Party, with its firm commitment to stop the expansion of slavery. Second, pro- and anti-slavery elements moved into Kansas with the intention of voting slavery up or down, leading to a raging civil war, known as "Bleeding Kansas." Abraham Lincoln targeted popular sovereignty in the Lincoln-Douglas Debates of 1858, leaving Douglas in a position that alienated Southern pro-slavery Democrats who thought he was too weak in his support of slavery. The Southern Democrats broke off and ran their own candidate against Lincoln and Douglas in 1860.
Read more about this topic: Popular Sovereignty