With this base line, and armed with the exit-poll data, we can get a pretty good estimate of how many whites, blacks, and Latinos cast ballots in both 2008 and 2012. Assuming the 72/13/10/5 percentage split described above for 2012, that would equate to about 91.6 million votes cast by whites, 16.6 million by blacks, 12.7 million by Latinos, with the balance of 6.3 million votes spread among other groups.
Compare this with 2008, when the numbers were 98.6 million whites, 16.3 million blacks, 11 million Latinos, and 5.9 million from other groups.
In other words, if our underlying assumption — that there are 7 million votes outstanding — is correct, then the African-American vote only increased by about 300,000 votes, or 0.2 percent, from 2008 to 2012. The Latino vote increased by a healthier 1.7 million votes, while the “other” category increased by about 470,000 votes.
This is nothing to sneeze at, but in terms of the effect on the electorate, it is dwarfed by the decline in the number of whites. Again, if our assumption about the total number of votes cast is correct, almost 7 million fewer whites voted in 2012 than in 2008. This isn’t readily explainable by demographic shifts either; although whites are declining as a share of the voting-age population, their raw numbers are not.