When Lincoln was first elected president in 1860 he supported a much different 13th Amendment, one which specifically stated that the US Congress is prohibited from abolishing or interfering with state controlled slavery. Lincoln opposed slavery in the territories because white laborers could not compete with slaves and white businessmen could not compete economically with slaveholders.

Lincoln, like many of his contemporaries, was more concerned with preserving the union than abolishing slavery. As the CSA was forming early in his first term, Lincoln supported the Amendment, which was passed by Congress and ratified by Ohio and Maryland, and would certainly have been ratified by 3/4 of the states. The movement came to an end with Fort Sumter.

Lincoln thought that a Constitutional Amendment that rendered Congress powerless on the issue of abolishing slavery would perhaps have averted a Civil War and restored the Union. He thought that as the nation eventually expanded, new states would eventually oppose slavery and state conventions would create an amendment some day abolishing slavery without congressional involvement. Nonetheless if Lincoln's original 13th Amendment had prevented the Civil War and restored the union, slavery would have been practiced in the US into the 20th century.

And his legacy would be different.