What factors led to close party competition in the 1880’s?

The question is not about a party called "the Close Party." "Close" is an adjective modifying the noun "competition." The question is about close competition between political parties. That is, it's asking why the two parties were getting about the same number of votes from the voters -- why the two parties were "close" to each other in the amount of support they got from people

This opening, called the Cumberland Gap, led from Virginia to the thickly forested land in present day Kentucky, In 1775, Boone helped build a trail called the Wilderness Road through the Cumberland Gap. The Cumberland Gap made it easier for colonists to move into the Ohio River Valley.