Missouri Statutes § 115.549 New primary election may be ordered, when

If any court trying a contested primary election determines there were irregularities of sufficient magnitude to cast doubt on the validity of the initial election, it may order a new primary election for the contested office. The order shall set the date of the election, which shall not be less than fourteen or more than thirty days after the order is issued, and shall be sent by the clerk of the court to each election authority responsible for conducting the special election. In its order, the court shall specify the name of each candidate for the office to be voted on at the special election, and the election shall be conducted and the votes counted as in other primary elections. Notice of the election shall be given in such manner as the court directs. The person receiving the highest number of votes at a special party primary election shall be his party's nominee for the contested office. The requisite number of persons receiving the highest number of votes at any other special primary election shall be the nominees for the office.