Mayors running mega-cities like Istanbul, Dhaka or Sao Paulo have budgets far in excess of many countries. But they also have a whole range of problems – from potholes to gargantuan traffic jams – that need sorting out here and now.
Different democratic systems (or otherwise) afford some mayors direct and indirect influence way beyond the geo-political jurisdiction. If that influence changes it could send ripples across the nations, continents and globe. This could be particularly significant where primary cities far outweigh the economic powers of secondary and tertiary cities – for example, in London. The @corecities recognise this and are grouping together to make an alternative and, most likely, a more sustainable proposition for their own good and for that of the nation as a whole.