A c.40% independent affiliation matches most of the country. What varies most from state to state is the proportion of Democrat vs Republican registrations (and the level of alternate party registrations). As one of the more "blue" states, there's a pretty big gap between the Dems and Reps, and the independent sector leans left, too. I'm still registered in Oregon (and vote via absentee ballot), am an independent since I loathe the Democratic Party, and generally vote left. Except fort the absentee part, I'm pretty typical of Oregon independent voters.

The dominance of Democratic representation from Oregon makes perfect sense given the state's political demographics, and any suggestion that the voting system has any effect on that is groundless conspiracy stuff. Rural Oregon is pretty conservative...but it's also largely unpopulated.

Mail-in voting is probably less subject to fraud than electronic voting machines are.