In case of the failure to qualify in his office, death, resignation, absence from the state, impeachment, conviction of treason, felony or other infamous crime, or disqualification from any cause, of both governor and lieutenant governor, the duties of the governor shall devolve upon the president of the senate pro tempore, until such disqualification of either the governor or lieutenant governor be removed, or the vacancy filled; and if the president of the senate, for any of the above named causes, shall become incapable of performing the duties of governor, the same shall devolve upon the speaker of the house.