I draw my conclusion from the fact that Lincoln was able to garner a majority of the northern votes in the 1860 election running on a "Preserve the Union" plank rather than a free the slaves promise. That was the northern War aim of the first two years of that Conflict. Lincoln's position on abolishion in that election was, as in previous debates, was rather vague, even including his 1861 Inaguration address. Whereas his stance of secession was quite clear and firm.
The 1860 Republican Party platform was very clear that they were against secession far more than it was for abolishion. Not all political issues of the 1850's were covered under the blanket of Slavery.