Final answer:
The Kansas-Nebraska Act led to political reorganization in the 1850s, significantly weakening the Whig party and contributing to its eventual demise, while precipitating the rise of the Republican Party and intensifying tensions that would lead to the Civil War.
Step-by-step explanation:
The passage of the Kansas-Nebraska Act had significant consequences on American politics, particularly the Whig party. After Congress narrowly passed the Act, political parties reorganized, and the Whigs experienced a decline in power. The Act divided the Democrats along sectional lines and led to the birth of the Republican Party, attracting northern Whigs, disillusioned Democrats, Free-Soilers, and abolitionists. Given the contentious political environment, the Kansas-Nebraska Act exacerbated divides over issues of slavery and immigration, paving the way for the eventual dissolution of the Whig party.
Furthermore, the Act's nullification of the Missouri Compromise's 36° 30' line allowed for the possibility of slavery expanding into new territories, sparking northern outrage and southern support. The subsequent violent events in Kansas heightened the stakes of the national debate over slavery. These events ultimately contributed to pushing the nation towards the Civil War and underscored the inability of the Whigs to navigate the country's changing political landscape.