But already in 1960 election Kennedy won almost all Washington and Oregon rural coast region counties, But he didn't win in Seattle and in Portland!
Radical or Socialist positions have a long history in the rural West. Just look at Debs', LaFollette's or Bryan's percentages there. (I think Bryan is where it started.) THe IWW's membership was mostly concentrated out there (though concentrated is maybe the wrong word). Eastern Washington is logging country, Northern California once was mining country, in other words, extremely bluecollar (Cowboys are another bluecollar population group...) So the question is not so much when it began, but why it died out on the interior but survived on the coasts. And here, I guess, supersoulty's immigrants come into play, though I think much more for North California than for Wash. & Ore. In other words: Leftie strongholds in the middle of the Utah desert died out, people moving to neighboring areas, people moving in, the young not taking up the idelogy from the old. But due to an influx of Left Wingers of a different sort, these ideas remained viable in the coastal areas. The two traditions kind of interbred. It's a rough outline of course, but I guess it's pretty much what happened.