The Kansas-Nebraska Act was a controversial bill that led to further divisions between North and South.  The bill allowed for settlers within a territory to make decisions about whether they wanted to allow slavery or not.  This change was buried within a bill that was about new territories, the future Transcontinental Railroad, and farmland.  

The bill was introduced in Congress by Stephen A. Douglas.  The primary purpose of the bill was to officially establish a new territory in the midwest.  Due to the location of this territory, it should have been a free territory according to the terms of the Missouri Compromise.  Wanting to gain the support of Southerners in Congress, Douglas proposed that the territory be split into two, Kansas and Nebraska.  This also led him to suggest that the settlers in the more southern of the two territories decide if they wanted to allow slavery or not.  This idea was called "popular sovereignty."  Kansas was established as a slave territory.  Northern opposition led to tensions.  Abolitionists had opposed the bill.  Slave owning settlers moved to Kansas.  Abolitionists also moved to Kansas in opposition.  An official legislature was established, and in opposition an unofficial one was also established in a different town.  Abolitionist John Brown murdered farmers who were proslavery, and eventually fighting broke out between abolitionists and those who believed in slavery.  It was a war on a small scale.  This time was later referred to as "Bleeding Kansas."  Tensions due to these events contributed to the rift between Southern and Northern states, which eventually led to the Civil War.

What effect did the Kansas-Nebraska Act have on Northern and Southern public opinion?

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.