The President of Council shall act as presiding officer of the Council in the absence or incapacity of the Mayor and during such absence or incapacity, shall exercise all the powers and duties granted the Mayor by the Charter. While presiding over special or regular meetings of Council the President of Council may vote upon all matters coming before the Council, but in no event shall the President of Council, in such person's dual capacity as Council member and presiding officer of Council, cast more than one vote on any action. In the event that the office of Mayor shall become vacant, the President of Council shall become Mayor for the unexpired term, and Council shall elect a successor from among the membership of Council to the office of President of Council for that unexpired term.