How can we have fair districts when voters from the same political party choose to cluster in the same area?

Some people argue that instead of blaming gerrymandering for causing partisan gridlock, we should blame the tendency of Democrats to cluster in major cities, allowing Republicans to take control elsewhere in the state. But that assumes that gerrymandered districts reflect the geography of counties and municipalities, which is the opposite of what gerrymandering does. 

Even if voters from the various parties are evenly distributed in an area, under the current system, politicians could easily gerrymander districts to reduce the impact of the opposing party.

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