'If You Live Near Other People, You're Probably a Democrat. If Your Neighbors Are Distant, Republican'

The below graph from Conor Sen, an armchair demographer in Atlanta, has been making the rounds this morning in my Twitter feed. It neatly reflects a political phenomenon we've written about before: Yes, cities generally tend to lean more Democratic, and rural states more Republican, but the fine-grained relationship between politics and population density is actually quite remarkable.

This scatter plot looks at congressional districts, which are ranked according to the Cook Parisan Voting Index. That measure essentially reflects how Republican or Democratic a district leans (by percentage of voters, not ideological purity) relative to the national average. A Democratic district shown above as +10, for example, gave the Democratic candidate in the last two presidential elections on average 10 points more of the local vote (say, 63 percent compared to 53 percent) than the nation-wide vote.