a. There was a breakdown of national politics into sectional rivalries over the issue of slavery.
Explanation:
One of the main characteristics of the political landscape in the country in 1860 was the fact that conflict over the issue of slavery was growing. Sectional rivalries were arising, both in the North and in the South. Moreover, the abolitionist movement was growing in popularity and strength. All of these factors made the political landscape of national politics difficult to navigate.
