Closed primaries, in states that are monopolized by one party (like Idaho or Oregon), allow relatively small, highly motivated, extreme groups to dominate their parties by allowing those groups to focus all of their resources on the primary election rather than the general election where they have to appeal to a broader electorate.
What this means is that closed primaries tend to drive the dominant party towards its highly motivated extremes, which is exactly what we see in states like Idaho and Oregon.
Open primaries draw parties away from the extremes because the parties have the same broad pressures in both the primary election and general election. If you are a fan of extreme politics on both sides and listen to the demonization of your neighbors coming from the mainstream (and other) media outlets like Fox News and MSNBC, then you should support closed primaries.
On the other hand, if you don’t think your neighbors are baby-eating communists or goose-stepping fascists, then you should support Proposition 1 and open primaries.
James Knobbs
Sandpoint