In a lot of cities especially, COIs will mirror sharp political divides. NYC is a prime example of this.
What do you mean by "political divides?" Simply looking at the D/R margin is not going to give you a lot of insight into the politics of most neighborhoods in NYC or Chicago, simply because they're so overwhelmingly Democrat. Big city politics tends to hinge on more nuanced divides around things like race, ethnicity, language, sexuality, class, etc.
There's no way to answer this question because concepts of community are subjective. Ask two people who live on the same block what constitutes their geographic "community", and they will possibly give you two very different answers. They'd both be correct.
