None. And Slavery was not needed in any of the states that allowed Slavery in 1860 either.
But, that wasn't the point. It was about the will of the people and what was legal for them to decide for themselves. It was about Legal process and the assurance that that process would be followed, and not mob rule in which the majority (the northern free states) did not exercise their power and devolve that political power into tyrany over the minority (the slave owners).
Lincoln repersented that northern mob rule mentality, and because of that you have South Carolina making the election of Lincoln as a secession issue. Note that South Carolina did not have a popular vote for president in 1860. The Breckenridge/Bell/Douglas tickets repersented the enternal conflicts over the complexity of the several ISSUES within the slavery debate and the states themselves and the country as a whole.
The Southern states were trying to find a way to remain in the Union in November 1860. But the election of Lincoln set the stages for the dissolution of the Union, once Lincoln demonstrated that he was willing to use illegal force to accomplish his purposes.
Remember that the most commonly used textbook in institutes of higher learning on Constitutional law, even in the United States Military Academy at West Point, taught that while secession was undesirable it was legal under the Constitution. Appearently a book that Lincoln never read, since he didn't attend West Point and didn't practise Constitutional Law.
The same was true of the practise of Slavery. It was undesireable, but it was legal. It is the same with the right to private ownership of guns. Many people do not wish to own one, and would like to regulate the private ownership of Firearms even to restrict or ban that private ownership.
Is owning a gun in your home a dire need today? Supposedly not, but it is still legal and there is sometimes a need.