Ohio Const. art. II, § 11

A vacancy in the Senate or in the House of Representatives for any cause, including the failure of a member-elect to qualify for office, shall be filled by election by the members of the Senate or the members of the House of Representatives, as the case may be, who are affiliated with the same political party as the person last elected by the electors to the seat which has become vacant. A vacancy occurring before or during the first twenty months of a Senatorial term shall be filled temporarily by election as provided in this section, for only that portion of the term which will expire on the thirty-first day of December following the next general election occurring in an even-numbered year after the vacancy occurs, at which election the seat shall be filled by the electors as provided by law for the remaining, unexpired portion of the term, the member-elect so chosen to take office on the first day in January next following such election. No person shall be elected to fill a vacancy in the Senate or House of Representatives, as the case may be, unless he meets the qualifications set forth in this Constitution and the laws of this state for the seat in which the vacancy occurs. An election to fill a vacancy shall be accomplished, notwithstanding the provisions of section 27, Article II of this Constitution, by the adoption of a resolution, while the Senate or the House of Representatives, as the case may be, is in session, with the taking of the yeas and nays of the members of the Senate or the House of Representatives, as the case may be, affiliated with the same political party as the person last elected to the seat in which the vacancy occurs. The adoption of such resolution shall require the affirmative vote of a majority of the members elected to the Senate or the House of Representatives, as the case may be, entitled to vote thereon. Such vote shall be spread upon the journal of the Senate or the House of Representatives, as the case may be, and certified to the Secretary of State by the clerk thereof. The Secretary of State shall, upon receipt of such certification, issue a certificate of election to the person so elected and upon presentation of such certificate to the Senate or the House of Representatives, as the case may be, the person so elected shall take the oath of office and become a member of the Senate or the House of Representatives, as the case may be, for the term for which he was so elected.