Mo. Rev. Stat. § 115.776: Caucuses, nomination for presidential candidates — delegates for national conventions.

The state party organization which is the state organization recognized by the national organization of that established political party shall, before the national convention, conduct a series of caucuses culminating in congressional and state conventions for the purpose of nominating a candidate for the president of the United States. Delegates to the national conventions shall be chosen at the congressional district and state conventions pursuant to rules established by the political parties.