in the 1840s as America expanded West the South wanted slavery to expand with it whether or not the government could actually stop or keep slavery from expanding into western territories that question actually becomes one of the heated questions of the 1840s and begins to really divide the nation by the 1850s Democrats tended to take the view of what was known as popular sovereignty which is that the territories ought to be open to slavery at the very least people in the territories ought to decide for themselves and that the decision shouldn't be made until they apply for statehood but in 1846 representative David Wilmot a Democrat from Pennsylvania proposed legislation which came to be known as the Wilmot Proviso that would ban slavery outright in any new territory one from Mexico in the mexican-american war the legislation triggered a split and the mostly pro-slavery Democratic Party and Wilmont was unable to get his proviso passed it went through the house but it did not go through the Senate the failed amendment greatly amplified the north-south split over slavery and pushed the country further towards civil war you