Answer :
Final answer:
Redistricting was the main reason why many incumbents lost in the 1990s.
Explanation:
The main reason why many incumbents lost in the 1990s is c) Redistricting. Redistricting refers to the process of redrawing the boundaries of electoral districts, which can be done by the majority party in the state legislature. This can result in incumbents being placed in districts that are less favorable to their reelection chances. It can also lead to a political party gaining an advantage by creating districts that are favorable to their candidates.
While lack of campaign funding, voter apathy, and strong party support can also impact elections, redistricting played a significant role in the loss of incumbents in the 1990s.