Political clustering is reflected in religious participation and even shopping choices. David Wasserman, of the nonpartisan Cook Political Report, recently calculated that 89 percent of the Whole Foods stores in the United States were in counties carried by Barack Obama in 2008, while 62 percent of Cracker Barrel restaurants were in counties carried by John McCain.

“If voters are seeking an explanation for hyper-partisanship and dysfunction, they ought to look down the street,” Mr. Wasserman said.

Reality is fascinating.