Except when Lincoln wrote, "If I could save the Union without freeing any slave, I would do it" in his 1862 letter to Horace Greeley.
Why don't you provide a bit more of the quote:
quote page 470/471 of Goodwin's "Team of Rivals"
"The most sensational criticism, however, came from Horace Greeley. He published an open letter to the president in the New York Tribune on August 20, which he entitled "The Prayer of Twenty Millions." Claiming to speak for his vast readership, he decried the policy Lincoln seemed "to be pursuing with regard to the slaves," which, "unduly influenced by counsels ... of certain fossil politicians hailing from the Border Slave States," failed to recognize that "all attempts to put down the Rebellion and at the same time uphold its inciting cause [slavery] are preposterous and futile." Lincoln decided to reply to Greely's letter, seizing the opportunity to begin instructing the public on the vital link between emancipation and military necessity. "As to the policy I 'seem to be pursuing' as you say, I have not meant to leave anyone in doubt," he began. "My paramount objective 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 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."
The Republican party was founded by antislavery men around 1854 to 1856. It was a new party forming at a time when the dominant parties were Whigs and Democrats. The abolition of slavery is the issue that gave birth the Republican party.
By May of 1860, the party was strong enough to elect its first president. That president was Abraham Lincoln. He after a contentious debate, Lincoln made a stunning come from behind win (he was fifth or worse in votes at the beginning) and was in the end nominated unanimously.
Now why do you think the Southerners threatened to secede if Lincoln was elected?
Looks like the concept of "priorities" evades you, stains.
This is Lincoln at his finest:
"Those who deny freedom to others, deserve it not for themselves; and, under a just God, can not long retain it."