Constitution of the State of Ohio Art. V, § 7

All nominations for elective state, district, county and municipal offices shall be made at direct primary elections or by petition as provided by law, and provision shall be made by law for a preferential vote for United States senator; but direct primaries shall not be held for the nomination of township officers or for the officers of municipalities of less than two thousand population, unless petitioned for by a majority of the electors of such township or municipality. All delegates from this state to the national conventions of political parties shall be chosen by direct vote of the electors in a manner provided by law. Each candidate for such delegate shall state his first and second choices for the presidency, but the name of no candidate for the presidency shall be so used without his written authority.