Immediately following the scheduled time of convening of the General Assembly following attack, the legislators then present shall take steps to determine whether or not the Speaker of the House of Representatives and the President pro tempore of the Senate are available for performance of the duties of their respective offices. In the event that the Speaker and the President pro tempore, one or both, may be found to be unavailable, the members of the House or Houses concerned shall promptly elect by majority vote of the members than present a member of their respective body or bodies for temporary emergency succession to the powers and duties, but not the office of Speaker and President pro tempore, one or both.