Americans elected Abraham Lincoln as the nation's first Republican president in November of 1860. Northern political leaders had formed the Republican Party only a few years before, in large measure to combat the spread of slavery. Southerners had long been wary of Northern hostility toward their "peculiar institution," and Lincoln's 1860 victory proved to be the last straw in this sectional rivalry that had deeply influenced American culture and politics since the earliest days of the republic. By the time of Lincoln's inauguration five months later, in March 1861, seven Southern states had announced their decision to secede from the Union. Lincoln rejected secession as unlawful and pledged that his government would continue to exercise its authority, as best it could, in the rebellious states. A crisis in South Carolina, the first state to secede, tested Lincoln's mettle in the opening days of his presidency. Federal troops still held Fort Sumter in Charleston harbor, but their supplies were running low. Lincoln would either have to evacuate the fort or risk war by sending provisions. The new president understood the weight of the choice he faced: nothing less than the survival of the Union was at stake.