The Daily Yonder, blog of the Center for Rural Strategies, has an interesting post about how Sen. Obama won the Democratic presidential nomination. In short: The urban South is what gave Obama his national primary victory.

Tim Murphy and Bill Bishop looked at 31 primary elections in 2008, leaving out the caucus states, candidate's home states (AR, IL and NY), and Florida and Michigan. Out of the remaining 31 contests, they see several themes:

* The South was the only region that Obama won. They note that "Obama lost three out of the four regions, winning only the large group of 13 southern states." They use the Census Bureau's definition of the South, which includes states we don't at the Institute (D.C., Delaware, Maryland and Oklahoma). But even taking those out, the argument remains true.

* Within the South, urban areas made the difference. As they write:

Within the South, Obama only won the cities, but that vote was large enough to wipe out Clinton's advantages across the rest of the country. Sen. Obama won southern urban areas with more than 60 percent of the vote, running up a 1.44 million vote margin. Most of Obama's advantage came from just 27 urban counties in the South.

* Sen. Clinton won rural voters across the country, and most exurban voters. Murphy and Bishop:

Sen. Obama won the urban South, the exurban West and the urban Midwest. He lost every other geographic grouping to Clinton.

The authors make some other interesting points, but their analysis seems thin given that they never mention the role of race, especially white and black voters. Clearly, the spatial regions Murphy and Bishop describe -- Southern cities (largely African-American), rural Appalachia (largely white) -- all closely correlate with racial demographics.

How can one talk about these places in an election where race played a central role, without mentioning the race of the people who live there? (Age, the other key factor in the 2008 primaries, isn't mentioned either.)

There is, however, one interesting tidbit on the Latino vote, which I haven't seen reported elsewhere:

Exit polls have shown Clinton winning the Hispanic vote, but she hasn't done particularly well in counties with above average Hispanic population ... Clinton lost urban areas with large Hispanic populations. She won rural counties with above average Hispanic populations with 60 percent of the vote.