The Oregonian has this op-ed by two leaders of the Independent Party. The op-ed defends the party’s decision to let independent voters vote in the Independent Party’s primary. An earlier op-ed had criticized the Independent Party, on the grounds that the party’s decision will cost money.
The op-ed by the Independent Party leaders also highlights a peculiarity in Oregon election law. Although Oregon permits fusion, and although it is easy for a major party to jointly nominate a candidate with a minor party (i.e., a party that nominates by convention, such as the Libertarian Party or the Pacific Green Party), it is very difficult for two parties that both have primaries to jointly nominate the same candidate. Such a candidate can’t have his or her name printed on the primary ballot of two different parties. The only way two parties that nominate by primary can jointly nominate a candidate is to have that candidate win one major party primary via write-in votes.
That Oregon policy is almost certainly unconstitutional. A bill to fix the problem, HB 3287, has not made any progress in the legislature this year. In 1999, the Third Circuit ruled that if a state permits fusion for certain kinds of parties, then it must permit fusion for all qualified parties. Also in 1986 the U.S. Supreme Court said in Tashjian v Republican Party of Connecticut that states must let parties nominate non-members if they wish.