Which incumbents decide not to run in 2018?

[Vega]

I think there is a slightly above average chance for freshman Senator that Hirono decides not to run again (a la Dan Coats). I imagine she'll serve another term, given how strapped Hawaii is for Seniority in Congress, but you never know. Ambition among young upstarts is always a thing in Hawaii, so she could get a serious or non-serious challenge from someone in the primary.