Lincoln was a significant player in the R. Party in illinois. The R party wanted to limit slavery from the territories. It was widely believed that the domestic institutions of the states could not be changed by the federal government under normal circumstances, but the status of Slavery could be controlled by the Congress.
Abolitionists saw that as a very small but perhaps achievable step toward elimination of slavery. Abolitionists wanted slavery abolished.
AND they wanted to punish all Southerners for it. Hence came Reconstruction.