1) That they intend to win election to a different office. This announcement alone qualifies as an abdication of their existing office. Merely in order to run for that further office will require their total involvement in a series of activities which will require them to cease performing the duties they were elected to perform. A willful abdication of their elected position.
2) That while they might appreciate the high honor bestowed upon them in their current elected role, it is not what they aspire to. Whether they win the new position and do not return, or lose the new bid and later return egg-faced, that have already let their constituents know that, given their druthers, they'd be elsewhere. A de facto abdication.
Slice it, dice it, spin it up, down or sideways, it is an abdication when you seek any higher futher/different office than the one you now hold.
Period.
%^(