David Brewster, a founding member of Post Alley, has a long career in publishing, having founded Seattle Weekly, Sasquatch Books, and Crosscut.com. His civic ventures have been Town Hall Seattle and FolioSeattle.
Two groups likely hold the key. One is Black Lives Matter, which has an issue-focus on police reform but needs to get some distance from its CHOP partners on the far/libertarian/utopian Left. The other group is labor, which is now the key driver of Seattle politics (by default).
Seattle got a little of this regional spirit, but never drank deeply. Our cultural institutions are instead quite derivative, which is more comforting for audiences and donors. Take away the New York dominance, however, and you might have more vitality at the regional level.
In 1885-1915, the state's formative period, "Washington attracted a prodigious share of radicals, socialists, and utopians," coming here because we were a state that welcomed radical change.
I once asked one of the original founders of the coffee company how it could be economical to have so many folks occupying tables for hours while spending a pittance on a cup of coffee-flavored milk drinks.
If Act I of the rise of Movement Left in Seattle was the 2019 city council elections, these protest marches are Act II. They will have an enduring effect on participants.
All this puts protesters in a tricky situation, playing with matches. Their issues and grievances typically have a tough time breaking through to media attention.
One decision is to give up on the Republicans, rather than trying to woo them into some marginal concessions, since they have obviously been "bought." The effort now is to unify the Left, not seek a center.