It is you who are incorrect. Speaking of the Republican platform in a June 1864 letter to the Republican party leadership accepting nomination for reelection, Lincoln stated the following:
"I will say now, however, I approve the declaration in favor of so amending the Constitution as to prohibit slavery throughtout the nation. When the people in revole, with a hundred days of explicit notice, that they could within those days, resume their allegiance, without overthrow of their institution...elected to stand out, such amendment to the Constitution became a fitting and necessary conclusion to the final success of the Union cause."
Lincoln went on to campaign on the passage of the 13th Amendment and in his annual message to Congress in December urged the House of Representatives to pass the amendment, noting that the elections had made it clear that the people wanted the Amendment passed out of Congress and the results of the election ensured that it would be passed once the new Congress was sworn in in January. And he proudly acknowledged that his home state of Illinois was among the first to ratify the Amendment in February 1865.
Two years later, President Lincoln wrote...
Please present the quote if full:
"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. I shall do less whenever I shall believe what I am doing hurts the cause, and I shall do more whenever I shall believe doing more will help the cause. "
And don't forget the next paragraph where he says, "I have here stated my purpose according to my view of official duty; and I intend no modification of my oft-expressed personal wish that all men everywhere could be free."
Now ask yourself if the preservation of one form of representative government over another was worth the lives of an entire generation.