Why did two in five Democratic voters in Kentucky and Arkansas vote against President Obama in their states' primaries on Tuesday? Why did roughly the same portion of West Virginia Democrats do the same two weeks ago? Different theories have been floated. Maybe it was Obamacare? Maybe it was Obama's environmental policies? After all, West Virginia Sen. Joe Manchin ran an ad in 2010 when he literally shot the bill. Maybe it has something to do with gay rights? These states are very culturally conservative. Maybe those factors played a role, but it's hard to ignore one: race. 

In 2008, before, obviously, Obama had a chance to enact any unpopular legislation, only 22 percent of counties in the U.S. voted more Republican than they did in 2004, the New York Times reported. As The New Republic's Alec MacGillis writes, "Keep in mind: this was at the peak of Obama's popularity... And yet he did worse in this region than [John] Kerry, who's not exactly Johnny Of The Ozarks." To understand these results, it helps to look at the numbers from the 2012 primaries in which Obama has received the biggest protest votes, as noted by Politico's Charlie Mahtesian, overlaid on a map of 2008 election results showing the few counties in the country where John McCain received a larger share of the vote in 2008 than George W. Bush got in 2004:

After polls started showing a Tennessee lawyer polling surprisingly well against Obama in Arkansas, Ouachita Baptist University political science professor Hal Bass suggested to NPR it was because Obama was a "very urban, very urbane individual." That style just doesn't match the more rural culture of Arkansas, he said. MacGillis agrees: 

The more complicated answer is that this region has been shifting away from the Democrats at the national level for more than a decade now, as the national party has become more identified with highly-educated elites -- a trend that Barack Obama accelerated because, well, he's a highly-educated elite.

But Mitt Romney, also a highly-educated elite -- not to mention a Mormon -- performed 10 points better in Tuesday's Republican primaries than Obama did in the Democratic primaries. Romney won all of Arkansas' counties and all of Kentucky's counties. And Romney's opponents were nationally-known politicians who've all won actual elections. 

Earlier polls about people's racial attitudes further explain why these states are different. Approval of interracial marriage is at an all-time high -- 86 percent approve nationwide, Gallup found in September 2011 -- but approval is lowest in the South, at just 79 percent. As the Economist noted earlier this year, certain states show the lowest rates of interracial marriage, despite high black populations. In Arkansas, 9.4 percent of marriages are mixed race, Pew finds that Arkansas and Kentucky have lower rates of mixed-race marriages -- 9.4 percent and 7.1 percent -- compared to the nationwide rate of 15 percent. Obama is performing worst in Rim South states, states that are culturally part of the South but have lower black populations than the Deep South. As Mahtesian pointed out earlier this week, Obama has performed much better in Deep South states where he benefitted from higher black turnout.