Okla. Const. Schedule, § 29
Any person who shall be a qualified elector of any county of a judicial district at the time of the election held to ratify this Constitution, and who shall, in all other respects, be eligible under the provisions of the Constitution, to be elected judge of the District Court of such district, shall be eligible to be elected judge of the District Court of such district at the first election held for the election of State officers.