The Kansas-Nebraska Act, intended by Stephen A. Douglas to strike a middle ground between the slave and free states rather intensified the slavery debate. Both slave and free advocates believed that the issue would be settled once and for all in Kansas, and moved people into the territory sympathetic to their side of the argument. As a result, the Kansas-Nebraska Act polarized pre-existing feelings about slavery. Instead of leading to a peaceful resolution, the Act solidified opinion on both sides and made war inevitable.
When two separate state governments were electedin Kansas, largely as a result of fraud on both sides, conflict seemed the only way to resolve the issue. Henry Ward Beecher, brother of Harriet Beecher Stowe and an ardent abolitionist, sent rifles to Kansas known as "Beecher's Bibles." When pro-slavery forces burned the town of Lawrence; John Brown launched a revenge attack, and hacked several pro-slavery people to death in front of their families. Armed conflict resulted in the deaths of over 200 people.
Politically, the Whig Party divided between the Cotton Whigs who supported the slavery cause; and the Conscience Whigs who opposed it. The Conscience Whigs later formed the Republican Party. The Democratic Party also split North and South over the slavery issue.
The main effect that the Kansas-Nebraska Act had on public opinion was to drive the North and the South farther apart. The Act made opinion in both the North and the South much more negative towards the other section of the country.
This change in public opinion can perhaps best be seen in the impact that the Act had on the political parties. The parties had been, up until the Act, nationwide entities with supporters in both sections. After the Act, however, the Whig Party split up and completely disappeared. Meanwhile, the Democratic Party underwent a split of its own with Northern and Southern wings emerging and becoming essentially different parties.
In ways like these, the Kansas-Nebraska Act caused public opinion in both the North and the South to turn against the other section.