That evening Lincoln gave his acceptance speech. In it he said, "If we could first know where we are, and whither we are tending, we could better judge what to do, and how to do it. We are now far into the fifth year, since a policy was initiated, with the avowed object, and confident promise, of putting an end to slavery agitation. Under the operation of that policy, that agitation has not only, not ceased, but has constantly augmented. In my opinion, it will not cease, until a crisis shall have been reached, and passed. A house divided against itself cannot stand. I believe this government cannot endure, permanently half slave and half free. I do not expect the Union to be dissolved--I do not expect the house to fall--but I do expect it will cease to be divided. It will become all one thing, or all the other. Either the opponents of slavery will arrest the further spread of it, and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction; or its advocates will push it forward, till it shall become alike lawful in all the States, old as well as new--North as well as South..."
Many historians believe that this speech cost Lincoln the Senate race. However, it set the moral tone for the country about an issue that had to be addressed. The ensuing Civil War divided the country, but in the end the union was preserved and the house stands free.
Source: Collected Works of Abraham Lincoln, edited by Roy P. Basler