One sentence in their Washington Post story fairly leaps out:
"The total number of white voters actually decreased between 2008 and 2012, the first such drop by any group within the population since the bureau started to issue such statistics."
America's white majority, which accounts for nine in 10 of all Republican votes in presidential elections, is not only shrinking as a share of the electorate, but it is declining in numbers, as well.
The Balz-Mellnik piece was primarily about the black vote.
Sixty-six percent of the black electorate turned out, to 64 percent of the white electorate. Black turnout in 2012 was higher by 1.7 million than in 2008. Hispanic turnout rose by 1.4 million votes.