Iowa Code § 49.12: Election boards.

There shall be appointed in each election precinct an election board which shall ordinarily consist of three or five precinct election officials. At the commissioner’s discretion, additional precinct election officials may be appointed to work at any election. Not more than a simple majority of the members of the election board in any precinct shall be members of the same political party or organization if one or more registered voters of another party or organization are qualified and willing to serve on the board.