Nate Cohn has an interesting post at NYT’s Upshot, “No, Obama Didn’t Win One-Third of White Voters in Deep South.” Cohn responds to Larry Bartels Washington Post (Monkey Cage) post on the topic, arguing that in 2012:

Reputable surveys such as the American National Election Study and the Cooperative Campaign Analysis Project suggest that Barack Obama won 30 to 35 percent of Southern white votes in 2012.

That estimate overstates the reality. As Cohn explains,

But the exit polls, conducted on Election Day of actual voters rather than post-election, show that Mr. Obama received only 28 percent of the Southern white vote. And the definition of the South in those polls is much larger than the region about which I was writing. The polls include states like Maryland, Florida, Delaware and Virginia — states that were separate from my argument. Without those more Democratic states, Mr. Obama’s share of the white vote in the remainder of the South drops significantly.

But Cohn uses a different calculation:

How did we calculate Mr. Obama’s support among white Southerners? First, we estimated the composition of the electorate in every county by race, using data from the American Community Survey and Current Population Survey. Then we estimated the number of nonwhite voters won by Mr. Obama using exit poll data, combining national exit-poll data with local demographic data. We then subtracted the number of nonwhite Obama voters from his overall support, leaving us with his support among white voters.
Is this method perfect? No. It would not work well when a racial group’s voting patterns vary greatly by region. But that’s not the case here. Most nonwhite voters in the South are black, and they all but uniformly supported the president (based on a variety of evidence, including returns in overwhelmingly black precincts). If there’s a county that’s 50 percent black where Mr. Obama won 50 percent of the vote, it’s not hard to figure out that Mr. Obama won very few white votes.
In the aggregate, we estimate that Mr. Obama won 16 percent of white voters in a broadly defined Deep South, including Louisiana, Georgia, Alabama, Mississippi, South Carolina, Tennessee, Arkansas and Texas. In the countryside, Mr. Obama tended to run behind these figures — often winning less than 10 percent of the white vote.
The estimates closely resemble the exit polls, where available. Our method also suggests that Mr. Obama won about 28 percent of the white vote in the broader South.

But I have to wonder if generalizations about “the south” and “the deep south” have much meaning anymore, particularly when talking about presidential elections. It’s really more about the individual states.
In Georgia, for example, President Obama won 45.48 percent of the vote in 2012. About 31 percent of Georgia voters were African Americans, who went about 9-1 for Democrats. Latinos were about 2 percent of GA voters, and they break about 2-1 Democratic. Asian-Americans are also increasing rapidly in GA. So a guestimate would be that about 15 of Obama’s 2012 GA percentage were white voters. So, approximately 24 percent of Georgia’s white voters cast their ballots for Obama in 2012. When that figure reaches 30+ percent, GA will be a blue state. It could happen sooner, as the percentage of white voters decreases.
Using a race-focused analysis, it seems likely that Dems are going to have a tough time in 2016 matching the African American turnout Obama received in GA in 2012. Conversely, a white Democratic Presidential candidate might do a little better with GA white voters. The “race factor” looks like a washout. Looking ahead, however, the effect of voter suppression measures could be pivotal in close races.
Virginia and Florida are already purple states in terms of statewide and presidential candidates, North Carolina is closing in on earning that designation and Georgia is headed that way at a good clip. There’s not much point in lumping these states together with the likes of smaller southern states like MS, AL, SC, AR or TN just to make some grand generalization about the region.
Democratic presidential candidates are going to have to work the hell out of VA, FL and NC and going forward, they probably should spend some time in GA. These states are as purple as WI, NH, MO and OH. Generalizations about the attitudes of white southerners are losing relevance for presidential and state-wide elections every day.