Final answer:
The best word to fill in the blank is 'protracted', meaning extended in time, indicating a long debate that led to important reforms linked to the historical congressional debates on slavery and state rights.
Step-by-step explanation:
The best word to fill in the blank is Protracted. The sentence indicates that the debate between the two senators bored some people, suggesting that it was long and drawn out. The word protracted means lasting for a long time or longer than expected, which accurately describes a debate that bores some people but also leads to important reforms.
The protracted debate between the two senators bored some people but also led to some important reforms. The word 'protracted' means extended in time or drawn out, and it best fits the context of the question, as it suggests a lengthy debate that could inspire boredom in some listeners yet still bring forward significant changes.
This description is apt for the historical debates in Congress which often were long and could lead to critical transformations in policies, particularly in the time leading up to the Civil War, where discussions about slavery and state rights were heavily contested and could evolve into extended and heated debates.