Regional differences come into play big time:
In 2012, Obama won only 10% of the white vote in Mississippi and 15% in Alabama. Overall, Obama won about 46% of the white vote outside the South and 27% of the white vote in the South - Nation 2/25/13
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==another one===
Southern white working class - 40 point margin for Romney over Obama, apparently 09/30/12
http://www.courier-journal.com/article/20120930/COLUMNISTS21/309300041/1001/Joseph-Gerth-Polls-suggest-Kentucky-voters-gone-South?odyssey=mod%7Cnewswell%7Ctext%7CHome%7Cp
(note this is a pre-election poll, not an exit poll, but interesting)
...poll conducted a few weeks ago by the Public Religion Research Institute in Washington, D.C., ... that poll found that
in the South, among white working class voters, Republican Mitt Romney leads Obama by the astounding vote of 62-22 percent
a 40 percentage point difference.
The poll defined working class as having less than a bachelors degree and being paid by the hour or by the job.
No other region in the country had anywhere near that differential.
In the West, Romney led
by just 5 percentage points among white working class voters.
In the Northeast, he
leads by 4 percentage points. And
in the Midwest,
Obama leads Romney by 8 percentage points among white working class voters.
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Also, marital status makes a huge difference, at least amongst the white folk:
American Mosaic Exit Poll - Romney's Share of the vote (this is a few results from the Reuters thing)
http://isteve.blogspot.com/2012/11/heres-other-exit-poll-data-that-nobody.html
Here is everything on his chart that includes whites (except white & religion):
Romney's share of the vote
65.0 Married white men ` ` ` ` 50.6 single white men
61.9 Married white women ` ` `44.3 single white women
63.3 married whites ` ` ` ` ` ` 47.5 single whites
58.1 Whites