Lincoln tacitly supported the Corwin Amendment to the Constitution, which passed Congress and was awaiting ratification by the states when Lincoln took office. That doomed amendment would have protected slavery in states where it already existed. A few weeks before the war, Lincoln sent a letter to every governor informing them Congress had passed a joint resolution to amend the Constitution.
Lincoln directed his inaugural address to the South, proclaiming once again that he had no inclination to abolish slavery in the Southern states: Apprehension seems to exist among the people of the Southern States that by the accession of a Republican Administration their property and their peace and personal security are to be endangered. There has never been any reasonable cause for such apprehension. Indeed, the most ample evidence to the contrary has all the while existed and been open to their inspection. It is found in nearly all the published speeches of him who now addresses you. I do but quote from one of those speeches when I declare that "I have no purpose, directly or indirectly, to interfere with the institution of slavery in the States where it exists. I believe I have no lawful right to do so, and I have no inclination to do so." — First inaugural address, 4 March 1861.