First instance body dealing with electoral disputes
Nauru
Answer
Court of general jurisdiction (including Supreme Court)
Source
Electoral Act 1965(2011), Part 6 Disputed Elections, p. 21
30 The Court of Disputed Elections
TheSupreme Court is the Court of Disputed Elections and shall, subject to this Part,hear and determine a petition.
http://aceproject.org/ero-en/regions/pacific/NR/nauru-electoral-act-1965-2011/view