Democratic stronghold loyal to the party above all else. Oregon has only voted for 4 Republicans since FDR: Eisenhower, Nixon, Ford, and Reagan. Eisenhower was extremely popular after WWII. Nixon was after LBJ's fuck ups. Ford was a win over Carter. And Reagan was just that popular. It's also had a democratic governor for almost 40 years. Even during Reconstruction, Oregon had Democratic governors for most of that time period.
As such, Oregon democrats have free reign to stomp all over third parties.