Answer:
They were opposed to the expansion of Slavery into new states
Step-by-step explanation:
The Kansas-Nebraska Act allowed the people in those territories to decide on the issue of slavery by popular sovereignty. Although the Republican Party did not advocate the abolition of slavery, they were opposed to the expansion of slavery into new states. The Republican Party was opposed to the Kansas-Nebraska Act because they did not want either state to be allowed into the Union as a slave state.