It isn't a fully functioning county, and has no elected county government. The only officer is the sheriff who is appointed by the Director of the HI Dept of Health which runs the county. The county is now designated a national historical park, and no new permanent residents are permitted. Eventually there will be no inhabitants and I presume HI (and the Census) will make whatever changes are appropriate then.
Ah, no new residents are permitted. So, that's why the total vote numbers have been declining steadily in that "county".