In the event the office of Mayor shall become vacant for any reason, the President of Council shall thereupon become the Mayor and serve for the unexpired term or until the beginning of the term of the successor duly elected as hereinafter provided. Such person shall also continue as a member of Council with all the power and duties of such member, including but not limited to the right to vote. In no instance shall the acting Mayor have a second vote on the same issue. Council shall have the power to declare a vacancy. Any resignation shall be effective when tendered.