An Oregon initiative called the “Voter Fairness Act” will begin to circulate soon. It would amend the State Constitution to say that there should be a system in which parties must either nominate by convention, or participate in a primary that is open to all voters. A party would decide 250 days before an election whether it wants to have nominees, but if it does, it can only nominate them by convention at its own expense. If it doesn’t want to do that, its candidates would run in a May primary in which candidates from all the non-convention parties would run. It would be up to the legislature to choose how many primary candidates would advance to the general election.
Here is the text, which is proposal 55.