Harriet Beecher Stowe's 1852 novel Uncle Tom's Cabin increased abolitionist protests by vividly depicting the moral evil of slavery, and Lincoln later credited it with starting the Civil War. The 1854 Kansas-Nebraska Act established popular sovereignty for deciding if new states allowed slavery, fueling violence as pro- and anti-slavery settlers fought for control, with over 200 deaths. Tensions rose further as the Pottawatomie Massacre and caning of Senator Sumner polarized sections. New political parties emerged divided over slavery and immigration.