Iowa Code § 145A.7

When a protesting petition is received, the officials receiving the petition shall call a special election of all registered voters of that political subdivision upon the question of approving or rejecting the order setting out the proposed merger plan. The election shall be held on a date specified in section 39.2, subsection 4, paragraph “a” or “b”, as applicable. The vote will be taken by ballot in the form provided by sections 49.43 through 49.47, and the election shall be initiated and held as provided in chapter 49. A majority vote of those registered voters voting at the special election shall be sufficient to approve the order and thus include the political subdivision within the merged area.