In the context of the debates over slavery, what did Lincoln argue regarding its expansion into territories?

Lincoln argued that slavery should not expand into new territories as part of his broader opposition to the institution's growth. His stance was rooted in the belief that the spread of slavery posed a threat to the ideals of democracy and the principles laid out in the Declaration of Independence, particularly the idea that all men are created equal.

During the debates with Stephen Douglas, especially in the Lincoln-Douglas debates, Lincoln articulated his fear that allowing slavery to spread would undermine efforts to preserve a free society and would cement the institution in a way that could be detrimental to the United States as a whole. He saw the expansion of slavery as a moral and political issue that could intensify sectional divisions and undermine the nation’s unity.

Lincoln’s position contrasted sharply with the views of those who advocated for popular sovereignty, which proposed that the decision to allow slavery in new territories should be determined by the residents of those territories. By arguing against the expansion of slavery, he positioned himself as a leader of the emerging anti-slavery movement, motivating a growing base of support for his platform and the Republican Party, which sought not to abolish slavery where it already existed but to prevent its spread into new areas.