Games : How to cope with local domination?

This question is mainly in context of playing Ingress in a city or metropolis.

Most important factor in this case is the number of active agents on the field. Once a faction has more players locally, everything is easier for dominant faction and more difficult for the other one. Getting gears, fielding quarters with heavily shielded portals, organizing big operations, having available people to counter opponents actions...

And especially, it is more difficult, under a heavy domination, for a newcomer to continue playing, and casual players are often discouraged and playing less and less. So the domination tends to perpetuate itself.

How do you cope with that ? What should be the priorities for dominated faction ? Do you have any strategy to reverse the situation ?