How does Stephen Douglas define the merits of popular sovereignty?

He was rather an optimistic type, who believed that the slavery question could be settled by a local vote in each territory coming up for admission to the USA. He also claimed that a state would automatically be free soil, unless there was active local legislation in favour of slavery.

He failed to see that one state voting at a time would bring all the bully-boys descending on that one area. That was what caused 'Bleeding Kansas'.