During the first or second year of cooperation, a referendum on the question of combination must be conducted. The referendum must be on a date called by the governing bodies of the units that propose to combine. The referendum must be conducted according to the Minnesota Election Law, as defined in section 200.01. If the referendum fails, the same question or a modified question may be submitted the following year. If the referendum fails again, the same question may not be submitted. Referendums shall be conducted on the same date in all local government units.