In the context of the United States presidential election of 1860, the candidates Abraham Lincoln and John Bell can be considered moderate, while John Breckenridge and Stephen Douglas can be considered the most radical.
Abraham Lincoln was the candidate of the newly formed Republican Party, which was anti-slavery but not abolitionist. His platform called for the containment of slavery in the existing Southern states, but not for its immediate abolition. John Bell was the candidate of the Constitutional Union Party, which sought to avoid the issue of slavery and preserve the Union through compromise.
On the other hand, John Breckenridge was the candidate of the Southern Democratic Party, which supported the expansion of slavery into new territories and the protection of the rights of slaveholders. He was considered the most radical candidate because of his strong pro-slavery stance. Stephen Douglas was the candidate of the Northern Democratic Party, which also supported the expansion of slavery but advocated for popular sovereignty, allowing each territory to decide for itself whether to allow slavery or not. He was considered radical because of his willingness to compromise on the issue of slavery and his support for the controversial Kansas-Nebraska Act, which sought to repeal the Missouri Compromise.
Overall, the election of 1860 was a pivotal moment in American history, as it highlighted the deep divisions over the issue of slavery and ultimately led to the secession of several Southern states and the outbreak of the Civil War.