

Congressman Hal Rogers (R.-Ky.) represents the whitest Congressional district in the nation. (Photo by Melina Mara/The Washington Post)

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.

You can see how this looks in the chart below, which plots one thin bar for every congressional district in the U.S., sorted by the white non-Hispanic share of the district population, and colored according to whether a Democrat or Republican holds the seat.

On the left side of the chart are districts with the lowest white non-Hispanic population share. These districts are overwhelmingly Democratic. The least-white district in the United States is New York's 15th, which lies within the Bronx and is held by Democrat Jose Serrano. In terms of ranking by non-white population share a Republican district doesn't show up until number 21 on the list - that would be Florida's 27th, a majority Hispanic district with a large Cuban population, held by Ileana Ros-Lehtinen.

10 least-white districts

District (Representative) Party Total pop. Non-Hispanic white pop. % white NY-15 (José Serrano) D 713,763 15,998 2.24 CA-40 (Lucille Roybal Allard) D 698,159 35,962 5.15 CA-44 (Janice Hahn) D 700,824 50,905 7.26 CA-34 (Xavier Becerra) D 704,381 66,927 9.50 NY-5 (Gregory Meeks) D 733,970 85,273 11.62 TX-29 (Gene Green) D 705,502 83,184 11.79 TX-9 (Al Green) D 696,093 85,896 12.34 FL-24 (Frederica Wilson) D 687,488 85,462 12.43 NY-13 (Charles Rangel) D 740,984 96,680 13.05 CA-51 (Juan Vargas) D 696,599 100,555 14.44

Republicans, on the other hand, are better represented on the right side of the chart. The whitest district in the nation (at 96.2%) is Kentucky's 5th, represented by Republican Hal Rogers. There are a fair number of Democrat-held districts over here too - seats in highly liberal but overwhelmingly white New England states like Maine and Vermont, as well as some seats in West Virginia and the Northern Great Lakes region.

10 whitest districts

District (Representative) Party Total pop. Non-Hispanic white pop. % white KY-5 (Hal Rogers) R 721,703 694,217 96.19 ME-2 (Mike Michaud) D 663,304 629,567 94.91 OH-6 (Bill Johnson) R 720,406 683,330 94.85 WV-1 (David McKinley) R 615,010 580,150 94.33 VT-1 (Peter Welch) D 625,498 589,350 94.22 ME-1 (Chellie Pingree) D 665,780 625,174 93.90 PA-18 (Tim Murphy) R 706,534 661,505 93.63 WV-3 (Nick Rahall) D 615,013 575,575 93.59 PA-5 (Glenn Thompson) R 705,633 659,708 93.49 PA-9 (Bill Shuster) R 704,950 658,990 93.48

Separately charting the distribution of Democratic and Republican seats yields an even clearer picture of the racial divide between the parties. The charts below show the number of seats by each district's white population at 10 percent intervals.

The Republican distribution is highly skewed toward seats with strong white majorities. About two-thirds of Republican House seats are in districts where the population is more than 70 percent white. The Democratic seats, on the other hand, are surprisingly balanced, with similar numbers seen on both sides of the distribution. Less than three-in-ten Democratic seats are in districts where whites make up more than 70 percent of the population.

These numbers neatly illustrate why House Republicans can afford to balk on immigration reform, and to talk about things like a "war on whites:" in general, there's very little disincentive for doing so. A sizeable majority of the House Republican caucus simply doesn't need to worry about appealing to minority voters, period.

Things are different in the Senate, where statewide races force politicians to appeal to more heterogeneous audiences, both in terms of ideology and race. For a sense of this, we can zoom out to the national level and look at racial breakdown of all constituents represented by Democrats and Republicans in the House and Senate.

Whites make up a little more than 50 percent of the total population of all House districts represented by Democrats. But whites represent 75 percent of all Republican House constituents. Party constituent populations in the Senate, on the other hand, are considerably more balanced. Whites make up 63 percent of all Democratic constituents, and 65 percent of all Republican constituents.

In the House in particular, Democrats and Republicans represent populations that are racially quite different. They are quite literally playing to two very different audiences when it comes to race.

Moreover, House Republicans' constituents are considerably whiter than even Senate Republicans' constituents. Conversely, House Democrats represent a less white coalition of voters than their counterparts in the Senate. These differences partly explain not only the vast ideological gulf between House Democrats and Republicans, but also the frequently fractious relationship between Republicans in the House and Senate.