Here Guelzo focuses on the effects of Lincoln-Douglas debates in exposing the irreconcilable split between Northern & Southern Democrats regarding slavery in the territories.
Without the debates Douglas may have gotten away with speaking out of both sides of his mouth on the subject.
Interesting to note the words of Senators Davis & Benjamin, not usually thought of as Fire Eaters, but here doing their bit to make Northerner Douglas unacceptable to Southern Democrats.
If Dred Scott is right (which I strongly dispute) about slaves being non-citizen chattel, then Davis and his "moderate" Southern Democrats logically are right - the Constitution would protect their "property" rights even in Northern free-soil states.
What it boils down to IMHO, is Lincoln was right, not Taney. The Union under the Constitution could not endure half slave and half free. Douglas has been trying to square a circle that cannot be squared and Freeport exposed him.
Taney thought Dred Scott would resolve the slavery issue once and for all. Instead, Dred Scott set up the split between Northern, Douglas, Democrats and Southern Democrats that would ultimately put Lincoln in the White House.