did not bind legislators to a policy of balance—that slavery could be excluded in a territory, as it was in the Northwest Ordinance of 1787, at the discretion of Congress. Thus Congress could restrict human bondage, but never establish it. The ill-fated Wilmot Proviso announced this position in 1846. The Proviso was a pivotal moment in national politics, as it was the first time slavery had become a major congressional issue based on sectionalism, instead of party lines. Its support by Northern Democrats and Whigs, and opposition by Southerners, was a dark omen of coming divisions. Senator Stephen A. Douglas proclaimed the third doctrine: territorial or "popular" sovereignty, which asserted that the settlers in a territory had the same rights as states in the Union to allow or disallow slavery as a purely local matter. The Kansas–Nebraska Act of 1854 legislated this doctrine. In the Kansas Territory, political conflict spawned "Bleeding Kansas", a five-year paramilitary conflict between pro- and anti-slavery supporters. The U.S. House of Representatives voted to admit Kansas as a free state in early 1860, but its admission did not pass the Senate until January 1861, after the departure of Southern senators. The fourth doctrine was advocated by Mississippi Senator (and soon to be Confederate President) Jefferson Davis. It was one of state sovereignty ("states' rights"), also known as the "Calhoun doctrine", named after the South Carolinian political theorist and statesman John C. Calhoun. Rejecting the arguments for federal authority or self-government, state sovereignty would empower states to promote the expansion of slavery as part of the federal union under the U.S. Constitution. These four doctrines comprised the dominant ideologies presented to the American public on the matters of slavery, the territories, and the U.S. Constitution before the 1860 presidential election. States' rights A long-running dispute over the origin of the Civil War is to what extent states' rights triggered the conflict. The consensus among historians is that the Civil War was fought about states' rights. But the issue is frequently referenced in popular accounts of the war and has much traction among Southerners. Southerners advocating secession argued that just as each state had decided to join the Union, a state had the right to secede—leave the Union—at any time. Northerners (including pro-slavery President Buchanan) rejected that notion as opposed to the will of the Founding Fathers, who said they were setting up a perpetual union. Historian James