Unless otherwise provided by county charter, at primary and general elections there shall be nominated and elected in each organized county of this state county officers as follows:
The terms of all such officers shall be four years, or until their successors have been duly elected and qualified. Nevertheless, the term of any county office, combined with another pursuant to § 7-7-1.2 or 7-7-1.3, shall expire on the first Monday of January following the ordinance authorizing the combination.
SDCL 7-7-1.1