Missouri constitution
Article III: legislative department
Section 46(a)

(2) To adopt by legislative enactment such other legislation as may be necessary
and proper for insuring the continuity of governmental operations. Notwithstanding
the
power conferred by this section of the constitution, elections shall always be called as
soon as possible to fill any elective vacancies in any office temporarily occupied by
operation of any legislation enacted pursuant to the provisions of this section.