Iowa Code § 45.2
The name of a candidate placed upon the ballot by any other method than by petition shall not be added by petition for the same office in the same election.
Other methods, chapters 43, 44
[C97, §1100; C24, §651; C27, 31, 35, §655-a18; C39, §655.18; C46, 50, 54, 58, 62, 66, 71, 73, 75, 77, 79, 81, §45.2]