The presidential electors shall meet at the office of the Secretary of the State at twelve o’clock, noon, on the first Monday after the second Wednesday of the December following their election and, as required by the Constitution and laws of the United States, shall cast their ballots for President and Vice President. Each such elector shall cast his ballots for the candidates under whose names he ran on the official election ballot, as provided in section 9-175. If any such elector is absent or if there is a vacancy in the electoral college for any cause, the electors present shall, before voting for President and Vice President, elect by ballot an elector to fill such vacancy, and the person so chosen shall be a presidential elector, shall perform the duties of such office and shall cast his ballots for the candidates to whom the elector he is replacing was pledged.