Delaware constitution
Article II
Section 6

Whenever there shall be a vacancy in either House of the General Assembly, by reason of failure to elect, ineligibility, death, resignation or otherwise, a writ of election shall be issued by the presiding officer of the House in which the vacancy exists, or in case of necessity in such other manner as shall be provided by law; and the person thereupon chosen to fill such vacancy shall hold office for the residue of the term. And whenever there shall be such vacancy in either House, and the General Assembly is not in session, the Governor shall have power to issue a writ of election to fill such vacancy, which writ shall be executed as a writ issued by the presiding officer of either House in case of vacancy, and the person thereupon chosen to fill such vacancy shall hold office for the residue of the term.