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…

Had the same number of white voters cast ballots in 2012 as did in 2008, the 2012 electorate would have been about 74 percent white, 12 percent black, and 9 percent Latino (the same result occurs if you build in expectations for population growth among all these groups). In other words, the reason this electorate looked so different from the 2008 electorate is almost entirely attributable to white voters staying home. The other groups increased their vote, but by less than we would have expected simply from population growth.

Put another way: The increased share of the minority vote as a percent of the total vote is not the result of a large increase in minorities in the numerator, it is a function of many fewer whites in the denominator…

My sense is these voters were unhappy with Obama. But his negative ad campaign relentlessly emphasizing Romney’s wealth and tenure at Bain Capital may have turned them off to the Republican nominee as well. The Romney campaign exacerbated this through the challenger’s failure to articulate a clear, positive agenda to address these voters’ fears, and self-inflicted wounds like the “47 percent” gaffe. Given a choice between two unpalatable options, these voters simply stayed home.