While the South moved towards a Southern nationalism, leaders in the North were also becoming more nationally minded, and they rejected any notion of splitting the Union. The Republican national electoral platform of 1860 warned that Republicans regarded disunion as treason and would not tolerate it: "We denounce those threats of disunion ... as denying the vital principles of a free government, and as an avowal of contemplated treason, which it is the imperative duty of an indignant people sternly to rebuke and forever silence." The South ignored the warnings: Southerners did not realize how ardently the North would fight to hold the Union together.
Main article: United States presidential election, 1860
The election of Abraham Lincoln in November 1860 was the final trigger for secession. Efforts at compromise, including the "Corwin Amendment" and the "Crittenden Compromise", failed. Southern leaders feared that Lincoln would stop the expansion of slavery and put it on a course toward extinction. The slave states, which had already become a minority in the House of Representatives, were now facing a future as a perpetual minority in the Senate and Electoral College against an increasingly powerful North. Before Lincoln took office in March 1861, seven slave states had declared their secession and joined to form the Confederacy.
