I am a fan of the book “The Big Sort” by Bill Bishop, professor at the University of Texas at Austin. In National Journal, columnist Charlie Cook agrees with the Big Sort theory. Cook writes:
“More voters might want to just look down their own street: Something remarkable has happened in the last two decades observed in [Bishop’s] 2008 book, The Big Sort, increasingly transient Americans have clustered into politically like-minded neighborhoods to an unprecedented degree. It’s not shocking that voters are choosing to live alongside neighbors who share their cultural values, but this choice makes opposing points of view seem more alien, suspicious, even threatening. In a growing number of congressional districts, it also means that the primary has supplanted November as the “real” election.”
“Seven years ago, in assessing the red/blue divide of the 2004 election, [Cook] observed that the worlds of Starbucks and Wal-Mart seemed almost mutually exclusive. Today, with both retail chains more ubiquitous, a voter’s proximity to Whole Foods versus a Cracker Barrel is probably a better partisan predictor (try finding a Whole Foods in Mississippi or a Cracker Barrel in Seattle). All the way down to the neighborhood level, strong evidence shows that this geographic homogenization is real and has serious consequences.”
“A recent study of Virginia precinct data by The Cook Political Report found that in the 1996 presidential election, 56 percent of voters lived in neighborhoods that voted within 10 points, in either direction, of the statewide result. Over the next three elections, this percentage steadily declined, and by the 2008 election, just 41 percent of voters lived in neighborhoods that fell within this swing range, a remarkable 15-point drop. The demise of the “swing precinct” was just as dramatic in off-year gubernatorial races over the same period.”
“This pattern is repeating all over the country, as socioeconomic gaps widen: Diversifying inner suburbs are becoming safely Democratic, and heavily white outer and rural areas are growing even more Republican. Independent voters are the big losers, even though the latest Gallup data indicate that a plurality of voters do not identify with either party. The partisans in their midst, however, increasingly tend to be of one party only, not a mix. So in more districts, independent voters who crave compromise are held hostage by crusaders on the right or the left posturing for a primary election.” …
“Within states, self-sorting means that polarization within Congress is likely to get worse no matter who wins the White House. Smart redistricting consultants in both parties have noticed that it’s much easier to gerrymander safe seats today than it was during the last round of redistricting 10 years ago. As one insider put it, voters have already “redistricted with their feet.” All that mapmakers have to do is “drag and drop” the lines.” 
The Starbucks vs. Wal-Mart and Cracker Barrel vs. Whole Foods point is very insightful, though one can over play the point (e.g. many poor and working class Democrats shop at Wal-Mart and plenty of Republicans have been known to sip a latte at Starbucks). The Chicago suburb of Naperville happens to have a Whole Foods, Cracker Barrel, Wal-Mart and plenty of Starbucks all in close proximity in a shopping district along busy Route 59. Or take a Republican-leaning suburb such as Hinsdale, Illinois (hometown of Republican US Representative Judy Biggert and a number of Illinois Republican political notables), a compact town of 17,349, which has both a Whole Foods and several Starbucks yet neither a Wal-Mart nor Cracker Barrel. Ditto for the neighboring town of Willowbrook, Illinois: Whole Foods? Check. Starbucks? Check? Wal-Mart? No. Cracker Barrel? No. Democratic area? No.
The existence of a Whole Foods is not quite a predictor of local voting patterns. The point cannot be taken too literally as it is a stereotype, though a directionally useful one. Cook’s point is correct in the big picture. American politics is less about income than politicians like to say; it is more about moral values, culture and worldviews. Starbucks and Whole Foods clearly cater to a younger, more affluent urban customer and the Democrat Party had been making in-roads in that demographic.
By the way, I’ve been to all four of the places more than once and oddly enough, visit both Starbucks & Wal-Mart a few times a month. Perhaps I can help bridge the partisan divide while enjoying a Venti-sized brewed coffee? Feel free to try our poll and add a Comment below about which stores you like and if it reflects your politics!