The reduction of two offices of associate justice abolished by section 480.01 shall become effective upon the first two vacancies occurring in that office on the supreme court. Each justice of the supreme court serving on August 1, 1983 may continue to serve until the justice is not elected or does not seek reelection. If a justice who was serving on August 1, 1983, is defeated for reelection by another person, that other person shall be deemed to have been in office as of August 1, 1983, for the purposes of this section.