(CNN)The geographic and demographic separation between the two political parties, and the two Americas, has reached a new peak in the House of Representatives.
This is why Republicans and Democrats aren't talking to each other in Washington
In the 116th Congress sworn in last week, Republicans and Democrats now control districts that represent virtual mirror images of each other across a wide range of key measures, from racial composition and education to income and age, a new CNN analysis has found.
House Democrats hold the vast majority of districts with more minorities and more college graduates than the national average, while Republicans are mostly confined to districts with more whites and fewer college graduates than the national average. Likewise, Democrats now control the vast majority of House districts that are younger, more affluent or contain more immigrants than the national average.
The widening trench between the two sides promises to further narrow the prospect of them reaching any common ground. For the Democratic majority, the new alignment may make it easier for them to reach consensus on many polarizing cultural issues -- from immigration to gun control -- but may open new splits on economic questions such as taxes and trade.
To illuminate the differences between the seats each party holds, CNN producer Aaron Kessler used census data to track some of the key characteristics of all 435 House districts. That exercise, employing data from the American Community Survey's 2012-2016 district-level estimates, produced a stark divergence between the 235 House Democrats and the 199 House Republicans (for the purpose of this analysis, CNN treated the North Carolina House seat enmeshed in allegations of voter fraud as vacant).
The divergence is apparent across every key measure.
In the new House, just over three-fifths of the Democrats represent districts where the minority share of the population exceeds the national average of 38%. Almost exactly 85% of House Republicans represent districts that are more white than the national average of 62%.
Almost three-fifths of the Democrats represent districts where the share of adults holding at least four-year college degrees exceeds the national average of 30.3%. Over three-fourths of the House Republicans represent districts with fewer college graduates than average.
Nearly three-fifths of House Democrats hold seats where the median income exceeds the national level of $55,322. Two-thirds of House Republicans hold districts where the median income lags below the national level.
Nearly 54% of the House Democrats hold seats where the median age is younger than the national level of 37.7. Almost exactly 60% of House Republicans hold districts that are older than the national median.
Just over three-fifths of Democrats represent districts where the immigrant share of the population (the portion of people born abroad) exceeds the national average of 13.2%. Over 90% of House Republicans represent districts with fewer immigrants than the national average. (These numbers do not include the 18 seats in Pennsylvania, where the immigrant population was not available for the state's recently redrawn districts.)
This deep and consistent separation culminates a sorting-out process that has steadily reshaped the House since the 1990s.
"The tectonic plates have been shifting for a few years now," said Ken Spain, a former communications director for the National Republican Congressional Committee.
As recently as the 2009-10 Congress, there was still substantial overlap between the kinds of House seats each party represented. At that point, Democrats still held nearly half the seats defined as mostly rural in the innovative system developed by the CityLab website to classify districts into six groupings on an urban to rural continuum. Democrats dominated the most urban seats, but the two sides were competitive in suburban areas.
In 2010, during the midterm election of President Barack Obama's first term, Republicans swept away dozens of small-town and rural Democrats. Through personal popularity, those Democrats had been holding on to seats with large numbers of blue-collar, older and Christian white voters who usually voted Republican in presidential elections. But they could not survive the backlash among those voters to Obama's aggressive first two years.
The November 2018 result is the bookend to that election. This election swept away dozens of Republicans from suburban seats with large numbers of minority or white-collar white voters or both who had been increasingly voting Democratic in presidential campaigns. Those Republicans, from Reps. Mimi Walters and Dana Rohrabacher in Orange County, California, to John Culberson in Texas and Barbara Comstock in northern Virginia, could not survive the backlash among their voters to Trump's tumultuous first years.
The losses for Republicans last fall were concentrated in more affluent and better-educated districts. Democrats won 43 seats that Republicans controlled in the previous Congress, while losing three seats of their own, for a net gain of 40 (pending the North Carolina result). Of the 43 seats that Democrats gained, 31 are in districts that exceed the national average in college graduates, according to Kessler's analysis. Incomes exceeded the national median in 35 of the 43 districts that Democrats captured.
After these sweeping gains, Democrats now dominate well-educated and upper-middle-class districts, many of them immersed in the information-age economy and connected to global markets. Before the November election, each party held almost exactly half of the 201 districts where incomes exceed the national median; now Democrats hold 136 of those seats, or just over two-thirds. Before the election, Democrats held 57% of the 182 seats with more college graduates than the national average; after the election, they hold almost exactly three-fourths of those seats (135). Similarly in the CityLab classification system, Democrats gained a net of 35 seats in the three most suburban categories and now lead in them by 166 to 51.
The election left the GOP in an even more precarious position in diverse America: It now holds only about 1 in 6 of the seats with more minorities than the national average and just 1 in 8 of those with more immigrants.
Republicans still control two-thirds of the House seats where whites exceed their share of the national population. That's less than their three-fourths in the previous Congress, but still much more than in 2009, when the two sides split such seats about evenly. The GOP edge in those seats is a reminder of the big challenges still confronting Democrats in places less touched by economic and demographic change. But in the House math, it isn't nearly enough to overcome the GOP weakness in diverse districts and its erosion in white-collar suburbs.