It is big cities that are complex enough to support the cheat. There are only a few cities where the citizenry is actually D, but the larger numbers provide believable cover for literally countless fake votes. The sheer numbers also makes it absolute murder to investigate instances of fraud.
Almost all states are red. It is big cities that spoil the states. Too many rats in a cage always leads to chaos.
It is big cities that are complex enough to support the cheat. There are only a few cities where the citizenry is actually D, but the larger numbers provide believable cover for literally countless fake votes. The sheer numbers also makes it absolute murder to investigate instances of fraud.