Our fundamental disagreement starts with this statement.
For the entire 19th century, the South had fought bitterly to maintain an equal number of slave states as free states so that the Senate was always balanced. That was behind all the capital letter issues in history books, The 1820 Missouri Compromise, the Compromise of 1850, the Kansas-Nebraska Act. Douglas offered that as a compromise in 1854 to promote northern railroad interests. To get it past the South, the bill repealed the Missouri Compromise banning slavery north of Missouri, leaving it to the settlers to decide later when the territories became states, popular sovereignty as the textbooks call it.
Both sides wound up hating the compromise, the North because it gave an opportunity for slavery where it had been banned and the South because early settlers were not likely to have any use for slaves on non-plantation farmland. They understood to their bones that every non-slave territory that became a state was fatal to their control. As soon as they lost the Senate, ending slavery was an achievable goal. Free-Soilers, who kept the name after the small third party of that name merged with the Republicans in 1854, also understood that blocking the expansion of slavery was the only way to destroy it. The result was five years of war commonly called Bleeding Kansas. John Brown’s 1856 massacre of proslavery men at Pottawatomie Creek was a call-to-arms for the South.
Provocations continued. The Dred Scott ruling in 1857 led Senator Jefferson Davis to demand “federal legislation to guarantee the extension of slavery in the territories” said Richard Kreitner in Break It Up: Secession, Division, and The Secret History of America’s Imperfect Union. Brown’s raid on Harper’s Ferry in 1859 inflamed (always the word used) the South. Southerners saw militancy everywhere they looked. A group called the Wide Awakes (the woke people of today have ancestry) staged uniformed marches of thousands in every large city, even Democratic New York. Wikipedia has the best one-liner on them. “The Wide Awakes never marched anywhere in the South in 1860, but they represented the South’s greatest fear, an oppressive force bent on marching down to their lands, liberating the slaves, and pushing aside their way of life.” Dozens of slaves were lynched in Texas as a result. And politicians fanned the flames. William Seward made a crucial speech just before the 1858 Congressional elections, the “irrepressible conflict” argument that “a revolution has begun” and that “revolutions never go backwards.” The speech was reported everywhere and made him the leading candidate for 1860.
How did the South respond? The 1860 election was deliberately lost by the South in order to provoke the war. Quoting William C. Davis in his Look Away! A History of the Confederate States of America.
If Southern Democrats refused to support the almost certain candidacy of Douglas in 1860, then their bolting from the party would hand the election to the exclusively Northern Republicans, and the election of a president who represented strictly sectional constituency could be enough to propel slave states into action.
There was nothing sophisticated in the scheme, nor was its operation a secret.
Far from being warring entities, the three non-Republican parties understood that their interests aligned. As Kreitner says, “A change of only a few thousand votes in New York could have swung the election.” That would have given Lincoln only 145 electoral votes with 152 needed to win. The election would have been thrown into the House, which the Republicans did not control. “At the last moment, Lincoln’s three opponents decided to form a “fusion” ticket to block the Republican in the state. Too little, too late.”
In short, there is little question that the issue of slavery was foremost on everyone’s mind and the country was split between those wanting to preserve it and those wanting to end it, despite the usual block of fingers-in-the-ears “we can’t hear you” in the middle. The 1860 election would decide the future of slavery in the country. It was designed to do so and achieved that goal, if not the way anyone thought would be the outcome.