What party was he affiliating with? What was Lincoln Douglas debate? 5.Buchanan recommending admission of Kansas as a slave state in 1858; by pursuing a proslavery agenda he had helping to split his party, nation. IV. Abraham Lincoln, Republican Triumph, 1858–1860 A. Lincoln’s Political Career4.Lincoln arguing that prohibiting expansion of slavery, gradual emancipation, colonization of freeing slaves were only practical ways to address issue. 6.Lincoln returning to politics after passage of Stephen 3.1858 duel for U.S. Senate, Stephen Douglas declaring his support for white supremacy, Lincoln, put on defensive by Douglas, advocating economic opportunity for blacks but not equal political rights.