Why was the kansas-nebraska act a bad idea?

The act established that settlers could vote to decide whether to allow slavery, in the name of popular sovereignty or rule of the people. Douglas hoped it would ease relations between the North and the South, because the South could expand slavery to new territories but the North still had the right to abolish slavery in their states. Instead, opponents denounced the law as a concession to the slave power of the South. The new Republican Party, which was created in opposition to the act, aimed to stop the expansion of slavery, and soon emerged as the dominant force throughout the North.