What was the major issue of the Lincoln-Douglas debates?

The major issue of the Lincoln-Douglas debates held in 1858 was the institution of slavery and its expansion into the Western territories of the United States. The two politicians, Stephen Douglas and Abraham Lincoln, had very different views on the matter. Stephen Douglas believed that states should be allowed to decide whether or not slavery should exist within their own borders. This became known as his doctrine of "popular sovereignty." Abraham Lincoln, on the other hand, believed that slavery was morally wrong and should be outlawed in the territories. In his closing speech at the seventh debate, Lincoln summarized this issue by stating, "A house divided against itself cannot stand." By this, he meant that if the country did not find a way to resolve the issue of slavery once and for all, it would eventually tear itself apart.