Lincoln was well known to oppose slavery vehemently, yet he said his first goal was preservation of the union. He was a politician - that's always important to remember about our sainted former Presidents. They weren't actually saints, just people trying to accomplish something, often against tall odds.
I think Lincoln might have considered carefully what his nation would actually go to war far. He might have found abolition wanting as a popular cause, even if it was in fact his real cause.
Marked “Private & confidential,” the letter instructed Kellogg to “entertain no proposition for a compromise in regard to the extension of slavery. The instant you do, they have us under again; all our labor is lost, and sooner or later must be done over. … Have none of it. The tug has to come & better now than later.”I wish I were confident that President Obama were flawed enough to do political battle for his beliefs.