Last instance body dealing with electoral disputes
United States
Answer
There is only one level of adjudication
Source
Constitution
Article 1. Section 5
Each House shall bethe Judge of the Elections, Returns and Qualifications of its own Members […]
https://www.constituteproject.org/constitution/United_States_of_America_1992.pdf
Procedures for Contested Election Cases in the House of Representatives
Application of State Law and State CourtDecisions to Committee Actions
[…]
In short, the Househas the final say over House contested election cases. […]
http://assets.opencrs.com/rpts/RL33780_20101104.pdf
