Iowa Code § 43.66
The fact that the candidate who receives the highest number of votes cast for any party's nomination for an office to which section 43.52 or 43.65 is applicable is a person whose name was not printed on the official primary election ballot shall not affect the validity of the person's nomination as a candidate for that office in the general election. However, if there is no candidate on the official primary ballot of a political party for nomination to a particular office, a write-in candidate may obtain the party's nomination to that office in the primary if the candidate receives a number of votes equal to at least thirty-five percent of the total vote cast for all of that party's candidates for that office in the last preceding primary election for which the party had candidates on the ballot for that office. If there have been no candidates from a political party for a seat in the general assembly since the most recent redistricting of the general assembly, a write-in candidate shall be considered nominated who receives a number of votes equal to at least thirty-five percent of the total votes cast, at the last preceding primary election in the precincts which currently constitute the general assembly district, for all of that party's candidates for representative in the Congress of the United States or who receives at least one hundred votes, whichever number is greater. When two or more nominees are required, the division procedure prescribed in section 43.52 shall be applied to establish the minimum number of write-in votes necessary for nomination. If the primary is inconclusive, the necessary nominations shall be made in accordance with section 43.78, subsection 1.
Iowa Code § 43.66