In Idaho, the Democrat holding the premier elective office in the state was, for a couple of years, David Bieter, the mayor of Boise - which is a nonpartisan office. We have Bieter's Democratic background on conclusive record because he served as one in the state legislature, not any other way. The fact of the mayor's office being nonpartisan probably was a help to Bieter's election and re-election.
The office of King County executive is also officially non-partisan, but here too the partisan background of most of the contenders isn't a big secret. Of the five candidates, four have been elected to office before, and their background as Democrats (in Fred Jarrett's case, of recent vintage, but nonetheless) is well established.
Susan Hutchison, the fifth candidate and a former news anchor at KIRO-TV, is a different matter, because she hasn't run for office, partisan or otherwise, before, and there's no party registration in Washington. So where does she fit into the picture?
She's been described as the Republican and the conservative in the race, which may not be helpful right now in King County - “I don’t think labels are helpful,” she told the Seattle Post-Intelligencer (in a story that highlighted how little she has specifically said about her views).
But the article also pointed out (while mentioning some prominent Democratic backers) her very close ties to Republican and conservative organizations.
The site PubliCola has been digging in further, pointing out "FEC records showing that Susan Hutchison’s campaign manager, Jordan McCarran, has worked for Mike Huckabee and Sen Sam Brownback."
Unhelpful to Hutchison (who because of her years on local TV might be the be the best-known of the five candidates) or not, looks like the labels may be going to stick.