Mo. Rev. Stat. § 115.097: Judge not to be absent from polls more than one hour — not more than one judge from the same party to be absent at the same time.

No election judge shall be absent from the polls for more than one hour during the hours the polls are open on election day. No election judge shall be absent from the polls before 9:00 a.m. or after 5:00 p.m. on election day. No more than one judge from the same major political party shall be absent from the polls at the same time on election day.