The Lincoln-Douglas Debate refers to a series of seven debates held in 1858 between Abraham Lincoln and Stephen A. Douglas during their campaign for the U.S. Senate from Illinois. These debates focused primarily on the issue of slavery and its expansion into new territories. Lincoln argued against the spread of slavery, while Douglas supported popular sovereignty, allowing territories to decide for themselves. These debates were significant in shaping public opinion and highlighting the moral and political divisions in the United States. Although Douglas won the election, the debates helped elevate Lincoln to national prominence, setting the stage for his future presidency.