What if instead of the slavocrats seceding to protect slavery, the North had seceded because they refused to continue to be associated with slavers?
Highly improbable. For white Southerners, especially in the Deep South, slavery protection was (or was presumed to be) an existential issue. There were large areas where slaves outnumbered whites. It was assumed by most whites that if the blacks were not under rigid control, they would rise up against the whites and destroy them.
In the Upper South, there were fewer such areas, but slave property was still a very large proportion of wealth, and slaveowners were socially and politically dominant. And even there the fear of slave insurrection was real. Nat Turner's Rebellion was in Virginia; so was John Brown's expedition.
The "Fire-Eaters" had been for years asserting that fanatical "abolition fiends" wanted to incite such insurrections. Now an anti-slavery President was going to take power, and they asserted that he would use the Federal government to subvert the authority of whites over the slaves. That created enough panic to get secession declared in the Deep South. The Upper South wavered, vainly hoping for some compromise to restore the Union. When that was impossible, they also declared secession.
Now turn it around. Outright abolitionists were a minority in the North. Lincoln got just under 55% of the vote in the North, and both he and the Republicans loudly disclaimed any intention of abolishing slavery; their pledge was only to restrict it to the South.
Lincoln voters, and even many Democrats, disliked slavery, and didn't want in their states, but most of them were indifferent to its presence in Southern states. Few of them considered that presence more important than the Union. It didn't affect them, or threaten to affect them, in any important way.
In fact, there were some abolitionists who in 1860-1861 declared that Southern secession was a good thing, because it purged the U.S.A. of slavery. They were vehemently denounced, and even jeered off platforms.
The only way that Northerners might consider secession over slavery is if the prohibition of slavery in their states was overriden, and slavery was brought in. That possibility was raised by Republicans in the wake of the
Dred Scott decision. The Supreme Court had found that the Constitution allowed slavery in all territories, regardless of what Congress or the residents of the territory wanted; neither had the power to deprive a slaveholder of his property. Republicans suggested that it was only a small further step to a ruling that no state could do so either.
That would mean slavery in all states.
If the Court made such a ruling, and
if at the time there was a pro-Southern President (either a Southerner or a Doughface), and
if there was a pro-slavery majority in Congress... then there might be enough resentment in some Northern states for secession.
But that set of circumstances seems impossible.
Dred Scott was blatant judicial overreaching, asserting a claim that hardly anyone had even thought of. It overturned the Missouri Compromise, which had passed with Southern votes and been accepted by Southerners for over 30 years. Only three years earlier, Southerners had rejoiced that the Kansas-Nebraska Act would modestly breach the Compromise by allowing settlers in that territory to permit slavery.
All apportionments of the House gave a majority of seats to free states, and it seems highly unlikely that there would be enough Doughfaces to form a majority so pro-slavery that they would enforce such a decision. It would not be
impossible - there were some, and a determined pro-slavery President could use patronage and other manipulation to make more - but very unlikely. (The Senate was more easily controlled by the South, since it was not proportional.)
That's what it would take to provoke Northern secession, and I don't see it ever happening.