After crunching the numbers, Sean Trende observes the following:

As a county’s Latino and college-educated population grows, so too does Romney’s vote share.

As a county’s evangelical population expands, Romney’s vote share declines. Interestingly, as a county’s African-American population expands, Romney’s vote share declines as well. Overall, the most strongly significant variable is the percentage of evangelicals in a county.

He offers a few tentative thoughts regarding what might be going on:

Why this is the case is open to interpretation. The simplest answer is anti-Mormon bias, but that seems a bit too easy. After all, the alternatives are a pair of Catholics. The other possibility — and this is a problem with regression — is that religion could be a stand-in for ideology, and that, regardless of self-identification, a self-described conservative evangelical Republican is significantly to the right of a self-described conservative who is non-evangelical. Or it could be some third possibility: Perhaps evangelicals and non-evangelicals alike in heavily evangelical counties vote against Romney for an additional reason.

The other interesting observation is Romney’s decreased vote share in African-American counties. Again, this is susceptible to many interpretations. It could be that those few African-Americans who vote in Republican primaries are simply voting like their white evangelical brethren. Or it could be that whites in heavily African-American communities are reacting to Newt Gingrich’s attacks on food stamps and such, just as Democrats imply.

The left-of-center journalist David Sirota observed that Hillary Clinton fared particularly well in states with populations that were more than 6% but less than 17% black. His interpretation was that black-white conflict has shaped the political culture of the various states, and thus the voting patterns of primary electorates:

On the left of the graph, among the states with the smallest black population, Obama has destroyed Clinton. With the candidates differing little on issues, this trend is likely due, in part, to the fact that black-white racial politics are all but non-existent in nearly totally white states. Thus, Clinton has fewer built-in advantages. Though some of these states like Idaho or Wyoming have reputations for intolerance thanks to the occasional militia headlines, black-white interaction in these places is not a part of people’s daily lives, nor their political decisions. Put another way, the dialect of racism–the hints of the Ferraro comment and codes of Bill Clinton’s Jesse Jackson reference, for instance–is not politically effective because such language has not historically been a significant part of the local political discussion. That’s especially true in the liberal-skewed Democratic primary.

On the right of the graph among the states with the largest black populations, Obama has also crushed Clinton. Unlike the super-white states, these states–many in the Deep South–have a long and sordid history of day-to-day, black-white racial politics, with Richard Nixon famously pioneering Republican’s “southern strategy” to maximize the racist segregationist vote in general elections. “But in the Democratic primary the black vote is so huge [in these states], it can overwhelm the white vote,” says Thomas Schaller, a political science professor at the University of Maryland–Baltimore. That black vote has gone primarily to Obama, helping him win these states by big margins.

It is in the chasm where Clinton has consistently defeated Obama. These are geographically diverse states from Ohio to Oklahoma to Massachusetts where racial politics is very much a part of the political culture, but where the black vote is too small to offset a white vote racially motivated by the Clinton campaign’s coded messages and tactics. The chasm exists in the cluster of states whose population is above 6 percent and below 17 percent black, and Clinton has won most of them by beating Obama handily among white working-class voters.

As for the role of Latino population share, consider the following 2005 analysis from demographer William Frey:

Another 1980s observation which holds perhaps even more in the late 1990s is the strong domestic net out-migration away from High Immigration metros. Of the nine High Immigration metros, eight experienced domestic out-migration in the late 1990s compared with only six in the late 1980s. Moreover, five of the six greatest immigrant gaining metros (New York excepted) exhibited higher domestic out-migration in the late 1990s. In fact, the 1995-2000 net domestic outmigration from metropolitan New York alone exceeded the combined net out-migration from the ten High Out-migration areas as shown in the third category on Table 1. The reasons for out-migration from these High Immigration metros are complex. However, the dominant immigration impact on their overall population change seems to be accelerating between the late 80s and late 90s. (See Figures 1, 2 and 3.)

But domestic out-migration followed a particular pattern:

One proposition, made after the 1990 Census, was that the influx of low-skilled immigrant residents and workers in these High Immigration areas may cause employment, housing, or other forms of competition for similarly situated residents and thus, could provide some motivation for the unique “downwardly selective” out-migration pattern from these areas. In contrast, those with college educations, and presumably more professional, higher paying jobs, were not in direct competition with these newcomers, and could better afford the upscale housing and communities that were available. Such “competition” explanations could still hold force, though, as shall be discussed, they would need to account for the new “downwardly selective” domestic out-migration of Hispanics.

The composition of the Anglo population in immigration magnet regions has changed over time. Native-born workers who compete with immigrants and who are impacted most heavily by rising housing prices have tended to migrate to low-cost regions. Native-born workers for whom less-skilled immigrants are complements rather than competitors, e.g., professionals keen to outsource household labor, have tended to remain, and indeed to migrate to regions with large foreign-born populations. This is an oversimplification, but it does point to at least part of what might be going on here: it could be that Anglos living in regions with large Latino populations are precisely the Anglos who are comfortable living in diverse environments and who have navigated skill-biased technical change reasonably successfully.