Mo. Rev. Stat. § 66.508: Majority vote required.

In the event that a majority of the qualified voters voting on the proposition in such county at such election approve the proposition, then the ordinance or order shall be in effect. If a majority of the votes cast by the qualified voters voting are opposed to the proposal, then the governing body of the county shall have no power to impose the tax authorized by sections 66.500 to 66.516 unless and until the governing body of the county shall again have submitted another proposal to authorize the imposition and collection of the tax, and such proposal is approved by a majority of the qualified voters voting thereon.