Lincoln made it clear during his days in office that preserving and reuniting the Union--not the abolition of slavery--was his foremost objective as president.
My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that. What I do about slavery, and the colored race, I do because I believe it helps to save the Union; and what I forbear, I forbear because I do not believe it would help to save the Union... (Wikipedia, Abraham Lincoln/Emancipation Proclamation)
He believed that outlawing slavery would be best for the Union and that the practice would eventually die out over the course of time.
With that said, no one man exceeded Lincoln's efforts to strangle slavery. He initially believed that preventing further westward expansion of slave states and territories would eventually eliminate slavery elsewhere. He considered a policy of "compensated emancipation"; the possible colonization of former slaves in Central America, the Caribbean and even Africa; and even "limited suffrage" for the more "intelligent" Negroes. Legislation included:
- Banning slavery on Federal-owned lands.
- 2nd Confiscation Act, freeing slaves of "anyone convicted of aiding the rebellion."
- The Emancipation Proclamation, which freed slaves in the seceded (Confederate) states but not in the remaining slave states of the Union.
- The Gettysburg Address, with its "proposition that all men are created equal," clarified his belief and future policies that black men and women should be treated equally to the white man.
- The Thirteenth Amendment, proposed by Lincoln but not ratified until after his death, banned slavery absolutely.