Best I can figure it was just a matter of Populism. Washington, Idaho, and the rest of the west was fairly receptive to Populist ideals and generally anyone who ran on those ideas got a decent portion of the state-wide vote.
Why he got only a reasonable size of the vote in those two states is confusing, but Washington was a Populist state. (Once or twice have Populists and Populist Democrats Governors of the state.)
(It looks like he got 1.16% of the vote in South Dakota and .7% in North Dakota and Montana. Small numbers, but it does seem like the Populism had alot to do with it. His support in Washington could just be to more urban areas in Washington state than other western/midwestern states or just different economic conditions.)
I'm not sure if that helped or if I'm just ranting. But you did give me an idea for a Washington Senator in my timeline.
