This was to determine the nominee was not the idea of Independent Party of Oregon.  It was required by state law.

Many of the IPO nominations were won by write-in votes, because no candidate appeared for that office on the IPO primary ballot.  The reason for that was the state law that prohibits anyone from being on the IPO primary ballot who had not been a member of IPO, continuously, for the 250-day period prior to the primary election.  The deadline to become an IPO member was thus September 10, 2015, only 3 weeks after IPO was certified as a major party entitled to participate in the May 2016 primary election.

This party membership duration requirement is no big problem for the established Democratic and Republican major parties, which have stables of potential candidates and over 1 million long-term members.   But it removed from the IPO primary the most likely source of authentic candidates: political newcomers who have not, 14 months in advance of general election: (continued)