Neb. Rev. Stat. § 32-557

All elective city, village, and school officers shall be nominated and elected on a nonpartisan ballot unless a city or village provides for a partisan ballot by ordinance. No ordinance providing for nomination and election on a partisan ballot shall permit affiliation with any party not recognized as a political party for purposes of the Election Act. Such ordinance providing for nomination and election on a partisan ballot shall be adopted and effective not less than sixty days prior to the filing deadline.