Answer:
Stephen Douglas was a Democratic politician in the mid-1800s, and one of President Abraham Lincoln's main political opponents throughout his career.
This man was in favor of the concept of popular sovereignty, understanding as fundamental the will of the citizenry when making relevant decisions that affected the lives of the inhabitants of each of the states.
Thus, Douglas believed that the legality or not of slavery in each of the states could not depend on a fictitious line (the Mason Dixon Line), but should depend on the will of the citizens of each state, who from their vote were able to determine the validity of slavery in their territories. Thus, Douglas did not directly support slavery as such, but allowed it to continue according to the criteria of each state electorate.
