Robert A. Divine, et al., The American Story, 3rd ed., vol. 1 (New York: Pearson Education, Inc., 2007), 369-370.
In the series of debates that focused national attention on the Illinois senatorial contest, Lincoln hammered away at the theme that Douglas a covert defender of slavery because he was not a principled opponent of it. Douglas responded by accusing Lincoln of endangering the Union by his talk of putting slavery on the path to extinction. Denying that he was an abolitionist, Lincoln made a distinction between tolerating slavery in the South, where it was protected by the Constitution and allowing it to expand to places where it could legally be prohibited. Restriction of slavery, he argued, had been the policy of the Founders, and it was Douglas and the Democrats who had departed from the great tradition of containing an evil that could not be immediately eliminated.