I do not associate the debate of "Popular Sovereignty" with any state admittance into the United States; only with the governance of a territory. I strongly disagree that the issue was over the admission of any free or slave States.
Douglas platform- "Inasmuch as differences of opinion exist in the Democratic party as to the nature and extent of the Powers of a Territorial Legislature, and as to the powers and duties of Congress, under the Constitution of the United States, over the institution of Slavery within the Territories: '
Breckinridge platform- "That when the settlers in a Territory, having an adequate population, form a State Constitution, the RIGHT OF SOVEREIGNTY commences, and being consummated by admission into the Union, they stand on an equal footing with the people of other States, and the State thus organized ought to be admitted into the Federal Union, whether its constitution prohibits or recognizes the institution of slavery."
David