Mo. R. Gov. Bar Jud. 10.16
The candidates entitled to have their names printed on the ballots at a run-off election, and no others, shall be as follows: (1) if the first election resulted in a tie for first place between two or more candidates, then said two or more candidates; or (2) the two candidates who received, respectively, the highest and next highest number of votes at said election; or (3) if one candidate stood in first place and two or more other candidates tied for second, then all of those who stood in first and second place. The names of those candidates who give written notice to the clerk of their withdrawal as candidates before the printing of the ballots shall not be printed on the ballots for a run-off election. No blank line for the writing in of a name shall appear on such ballot.
Mo. R. Gov. Bar Jud. 10.16