what does the author mean in saying that popular sovereignty undermined the Missouri compromise

Answer 1

The author is likely suggesting that the idea of popular sovereignty, which allows residents of new territories to decide for themselves whether to allow slavery, directly contradicted the principles of the Missouri Compromise. The Missouri Compromise, passed in 1820, aimed to maintain a balance between free and slave states by prohibiting slavery in certain territories while allowing it in others. However, popular sovereignty effectively allowed for the expansion of slavery into previously restricted territories, undermining the compromise's efforts to regulate the issue of slavery in the United States.