California Code, Government Code - GOV § 12058

In case of vacancy in the office of Governor and in the office of Lieutenant Governor, the last duly elected President pro Tempore of the Senate shall become Governor for the residue of the term; or if there be no President pro Tempore of the Senate, then the last duly elected Speaker of the Assembly shall become Governor for the residue of the term; or if there be none, then the Secretary of State; or if there be none, then the Attorney General; or if there be none, then the Treasurer; or if there be none, then the Controller; or if there be none, then the Superintendent of Public Instruction; or if there be none, then the Insurance Commissioner; or if there be none, then the Chair of the Board of Equalization; or if, as the result of a war or enemy-caused disaster, there be none, then such person designated as provided by law.  In case of impeachment of the Governor or officer acting as Governor, the Governor's absence from the state, or other temporary disability to discharge the powers and duties of office, then the powers and duties of the office of Governor devolve upon the same officer as in the case of vacancy in the office of Governor, but only until the disability shall cease.