What was the idea behind popular sovereignty in the mid-1800s?

The idea of popular sovereignty was used multiple times in the mid 1800s. The goal of this concept was to allow new territories applying for statehood in the US to vote on whether or not the citizens wanted the institution of slavery to exist. This concept was supposed to be a peaceful way for individuals to decide on the issue of slavery.

However, this plan backfires when it is used in Kansas. The Kansas vote on slavery results in mass voter fraud and eventual violence.