Who is Stephen A. Douglas from The Fiery Trial: Abraham Lincoln and American Slavery and what is their importance?

Stephen A. Douglas was a politician during the same period in which Lincoln was politically active. In the 1850s, Douglas was a senator from Illinois. Douglas was a supporter of territorial expansion and the Mexican War. Douglas also supported the expansion of slavery into new territories, something Lincoln opposed. When President Buchanan suggested that the Dred Scot decision suggested that slavery was legal in every state of the union and he attempted to bring Kansas into the union as a slave state, Douglas surprisingly opposed him because it was against the wishes of the majority of the residents in Kansas. Douglas was a strong supporter of popular sovereignty and used this as an explanation for his stance.