Iowa Code § 49.18: Vacancies occurring on election day.

If, at the opening of the polls in any precinct, there shall be a vacancy in the office of the precinct election official, the vacancy shall be filled by the commissioner or, with the commissioner’s approval and for that election only by the members of the board present, consideration being given to the political party affiliation of the person appointed if necessary in order to comply with the requirements of sections 49.12 and 49.13.