Answer
popular sovereignty, also called squatter sovereignty, in U.S. history, a controversial political doctrine according to which the people of federal territories should decide for themselves whether their territories would enter the Union as free or slave states.
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Who proposed the idea of popular sovereignty?
In 1854, Democratic Senator Stephen A. Douglas, of Illinois, the chief proponent of popular sovereignty. Courtesy of the Library of Congress. Popular sovereignty in 19th century America emerged as a compromise strategy for determining whether a Western territory would permit or prohibit slavery.