As a result of the Kansas/Nebraska Act 1857. Kansas was a territory but the slavery status was not concluded. The situation called "Bleeding Kansas" emerged. Proslavery "border ruffians" from Missouri were entering the territory, attempting to "pack" the territory with proslavery citizens. Two territorial governments emerged. One proslavery the other anti-slavery. Presidents Pierce and Buchanan admin's. recognized the Pro-slavery government. This government had been elected fraudently, with proslavery legislators, and the illegals from Missouri. The Federal government knew the Territorial Gov. was fraudulent but chose to do nothing. Slavery was the issue. Senator Stephen Douglas argued for "popular soveriegnty" in territories. The population would decide the slavery status. Republicans (Lincoln's Party) opposed the territorial constitution, and even Douglas (Democrat) broke from his party on the constitution. So why were they so opposed to the Lecompton Constitution? For Douglas it would make his popular soveriegnty position meaningless. He opposed it not in the test of freedom, but in his political position of popular soveriegnty. Republicans general position was that there should be no further extension of slavery into new territories; slavery was a moral wrong. Douglas was in a curious manner in agreement with the Republicans. Here is why they opposed the constitution: The pro-slavery legislature allowed the people of Kansas territory to vote on one single clause...to allow slavery or not in the territory. But, on all other clauses/items of the constitution, inclusive of a clause that guaranteed all the property rights of slaveholders which already were in Kansas.......would simply go into effect without popular scrutiny or approval. The constitution emerged from effects of the Dred Scott, Supreme Court decisions, the de facto repeal of the Missouri Compromise of 1820 and the illegal movement of pro-slavers from Missouri (a slave state), moving into Kansas to vote and then return to Missouri. This period of American History is a really critical time to understand if your want to understand the emergence of the Civil War, and have a better insight into some contemporary events and processes.