Writing in the Brookings Institution's FixGov blog last week, political scientist Christopher Parker pondered House Republicans' stubborn refusal to back immigration reform, despite support in the Senate and across wide swaths of the conservative commentariat. He surmises that House Republicans are balking because they "represent constituencies haunted by anxiety associated with the perception that they’re 'losing their country' to immigrants from south of the border."Recent polling backs this up. Significant numbers of conservatives, and white Americans in general, admit to feeling discomfort at the prospect of a non-majority white America. These views are even stronger among Tea Party-aligned conservatives. According to Parker's polling, nearly two-thirds of Tea Party conservatives want to eliminate birthright citizenship, and 82 percent of Tea Partiers say they feel "anxious or fearful" about undocumented immigrants.Another factor behind Republican recalcitrance on immigration and similar issues is the simple racial math underlying many House congressional districts. According to U.S. Census data, only 13 out of 234 Republican-held districts are majority-minority (that is, districts where white non-Hispanics make up less than 50 percent of the population). That's about 5 percent of all Republican districts. In contrast, fully 49 percent of Democrat-held districts are majority-minority.[95% of Republican House districts are majority-white, by Christopher Ingraham, Washington Post, August 12, 2014]Three points.