In the Election of 1800, there were 3 pro-slavery candidates and one anti-slavery candidate, which was Abraham Lincoln.
When Abraham Lincoln won the election without winning over even a single state in the South, Southerners were angry and felt like they would have no power in this new government.
Even though Abraham Lincoln promised not to remove slavery in states which already had it, South Carolina seceded from (left) the Union almost immediately after, and six other states had also left the union to form their own Confederate States of America by the time Lincoln came into office.