Idaho Code § 59-408
In the event any county elective official shall be unable to serve, due to illness, injury or on account of war, war industries, job freezing or being a member of any branch of the armed forces of the United States of America, it shall be the duty of the county commissioners to appoint a qualified person to temporarily discharge the duties of the office as an acting officer. If possible, the person appointed must be chosen from the same political party as that of the elective official who is unable to serve.
This appointment shall remain in full force and effect until the duly elected official shall be able to assume the duties of his office. Providing, however, that no person so appointed by the commissioners shall receive remuneration different than that which would have been received by the elective official, whose place the acting officer is filling; and provided further, that no acting officer appointed shall serve a term longer than that for which the elected official was chosen.
Idaho Code § 59-408