Final answer:
The South was worried that Lincoln's presidency would threaten the institution of slavery, which was integral to their way of life, leading to the Secession Crisis and ultimately the Civil War.
Step-by-step explanation:
After Lincoln's election to the presidency in 1860, the South was deeply worried about the Republican administration's stance on slavery. This anxiety was fueled by the belief that Lincoln's victory would lead to the end of the institution of slavery and disrupt the southern way of life, even though the Republicans had not explicitly aimed to abolish slavery where it already existed. The southern leaders suspected that Republican abolitionists might use violent measures, echoing John Brown's tactics, to disrupt slavery in the South. State leaders like William Yancey warned that an end to slavery would be detrimental to the South, and Kentucky's John J. Crittenden noted that many southerners felt their only choice was to secede if the Republicans won.
These fears led to the Secession Crisis, with South Carolina being the first to secede, soon followed by other southern states, cumulatively leading to the formation of the Confederate States of America and the onset of the Civil War.