Abingdon, Virginia (CNN) A tale of two Virginia districts explains why the geographic, demographic and cultural chasm between the parties in the House of Representatives is about to grow much wider -- with ominous implications for America's escalating political tensions.

In the affluent, diverse, 10th Congressional District of Virginia in the Washington suburbs, a sharp backlash against President Trump has left Republican Rep. Barbara Comstock as perhaps the nation's most endangered GOP incumbent. Simultaneously, in the preponderantly white, working-class and rural 9th Congressional District of Virginia, which includes this picturesque town in the state's far southwestern corner, Trump's popularity is reinforcing the strength of Republican Rep. Morgan Griffith, who captured the seat from a veteran Democrat during the GOP landslide of 2010.

The contrasting prospects for Comstock and Griffith crystallize how the 2018 election could complete the geographic restructuring of the House that first fully snapped into view during that GOP sweep eight years ago.

We have had two countries for a while, but it is as if, appropriately enough under Trump, the walls are being raised. They are higher than ever.

In 2010, amid a sharp backlash against President Barack Obama, the GOP ousted dozens of House Democrats from small-town and rural districts; the casualties included many who had held their seats for decades, like Rick Boucher, the longtime Democratic representative from the 9th District who Griffith beat. Now the GOP faces the inverse risk: Democrats in November could sweep out 20 or more House Republicans like Comstock from districts centered on white-collar suburbs around the nation's biggest cities where Trump is unpopular.

"This could be very easily be a mirror image election (to 2010) from the Democratic side," says Rep. Tom Cole of Oklahoma, a leading House Republican strategist.

The biggest question for November, of course, is whether Democrats will gain the 24 seats they need to recapture the House majority. But whether or not they do, November could produce a realigning election that remakes the composition of the parties' coalitions in the House. Just as 2010 triggered an extended period of Republican advantage in small-town and rural districts, 2018 could do the same for Democrats in white-collar seats inside the largest metropolitan areas.

The trench separating red and blue America

In suburbs and rural areas, a lot of congressional districts used to split their votes between congressional and presidential elections. That's not happening nearly as much. A wave in 2010 swept a lot of Democrats out of rural areas. The same could happen in 2018 with Republicans in suburbs.

The result would be a geographic separation in the House as stark as any in modern times. Democrats seem likely to emerge from this fall's election with a clear upper hand in highly urbanized House seats that are racially and religiously diverse, disproportionately white-collar and secular and connected to the globalized information economy. Republicans, in turn, could remain dominant in districts outside of urban centers that are preponderantly white, heavily blue-collar, more religiously traditional and reliant on manufacturing, agriculture and resource extraction. The ideological, demographic, economic and even physical distance between the coalitions -- the trench separating red and blue America -- could be even greater than it is today.

"You look at the map -- and any (place) that has a disproportionately rural electorate -- and you can count it as Republican in any election, and the opposite is true in those suburban/urban" areas, says Larry Sabato, a University of Virginia political scientist. "We have had two countries for a while, but it is as if, appropriately enough under Trump, the walls are being raised. They are higher than ever. And I'm afraid that is going to be even more true in 2020 than in 2018."

As opposed to a wave, this looks like a realignment and that's scarier. Former Republican Rep. Tom Davis

This accelerating separation leaves both parties in a precarious position. Many Republicans worry that under Trump they are losing support in the places that are adding population and jobs and increasingly relying on the places that are shrinking or stagnating on both fronts.

"As opposed to a wave, this (election) looks like a realignment and that's scarier," says Tom Davis, a former Republican representative from Northern Virginia, who chaired the National Republican Congressional Committee during his years in the House. "That is a bigger problem for Republicans long term, because we are winning the places that are not the growing tide (in population), they are the shrinking tide, and that's not where you want to be."

Some Democrats, in turn, fear that even greater dominance of the largest metropolitan areas will still leave them operating with too narrow a geographic base of support to consistently control majorities not only in the House, but also in the Senate and the Electoral College. In 2016, after all, Hillary Clinton won the popular vote by obliterating Trump in the largest places -- she won 87 of the 100 largest counties by more than 15 million votes combined -- yet Trump carried the Electoral College by routing her outside of the big urban areas in enough of the battleground states, from North Carolina and Florida to Michigan and Wisconsin.

"If you can combine a ... respectable showing in some of these other areas of the country with obviously growing strength in urban and inner suburban areas and white-collar constituencies, then you have a winning formula," says long-term Democratic strategist Ruy Teixeira. "The strength in these (metropolitan) areas can be canceled out by the structural problems in these other (small-town) areas."

The divergent dynamics separating suburban and small-town America are neatly encapsulated in Virginia's 9th and 10th congressional districts. Though each is now represented by a Republican, the two places could hardly be more different. Whites represent almost 90% of the population in the 9th District, but only about 61% in the 10th. Immigrants (largely Hispanic and Asian) represent over 20% of the population in the 10th but less than 3% in the 9th. Just over half of the adults in the 10th District hold at least a four-year college degree, compared with only about 1-in-5 in the 9th. The median income in the 10th, at $120,384, is nearly triple its level in the 9th, less than $42,000.

Class inversion

The fact that Democratic prospects are rising in the district that is more affluent, better-educated and more racially diverse and are sagging in the district that is the opposite on each count testifies to the larger shifts that have remade the two parties' electoral coalitions over the past several decades. Particularly since the 1980s, the parties have experienced what I've called a "class inversion," with Republicans growing stronger among the blue-collar whites who anchored the Democratic coalition for decades after World War II and Democrats adding growing competitiveness among white-collar whites (especially women) to their traditional advantages among nonwhite voters.

Typically, such changes in electoral behavior have been felt at the presidential level long before they filter down to congressional races. Republicans, for instance, started consistently winning Southern states at the presidential level in 1972 but didn't capture a majority of the region's congressional seats until 1994. Similarly, while Republicans built a solid advantage in small-town and rural areas at the presidential level starting in 2000, they did not immediately beat many of the House Democrats representing those areas.

These divisions don't start in Washington DC and come down; they are in the country and working up. Republican Rep. Tom Cole

Instead, the watershed election came in 2010 for rural and small-town Democratic House members such as Rick Boucher, who had held his Southwest Virginia seat for nearly 30 years. Boucher had deep roots in the district: He was born in Abingdon, and his grandfather had represented the area in the Virginia House of Delegates. He still remembers the town when it followed more bucolic rhythms.

"It was a place where farmers came to market and brought their goods," Boucher told me recently in an interview in the backyard of his home on Abingdon's peaceful main street. "The downtown on Saturdays was packed. People were walking from one end of town to the other."

Boucher represented the area in the Virginia state Senate for eight years, and then in 1982 he beat a longtime Republican incumbent to win the area's congressional seat. Boucher had a close squeeze in 1984, when he narrowly survived the Ronald Reagan landslide to win a second term. After that, he won re-election to Virginia's 9th Congressional District 12 more times, never capturing less than 59% of the vote, even as his culturally conservative, coal-producing and rural district steadily tilted its votes toward Republican presidential candidates. Republican presidential nominees George W. Bush in 2004 and John McCain in 2008 each carried nearly three-fifths of the district.

Swept out in a wave

Former Democratic Rep. Rick Boucher lost his rural Virginia seat in 2010.

Boucher survived by avoiding cultural conflicts wherever possible (he opposed President Bill Clinton's key gun-control initiatives, for instance) and concentrating on bread-and-butter economic concerns.

"What I was doing through all of those years was attracting federal funds to build industrial parks, water systems, wastewater systems. I developed my own program for attracting industry," he recalls.

But in 2010, Boucher's string ran out. Obama's first two years had stirred a huge conservative backlash in the district, with both the Affordable Care Act and the legislation passed by House Democrats to limit the carbon emissions linked to global climate change emerging as powerful flashpoints. Republican nominee Griffith, a former GOP majority leader in the state House, particularly emphasized Boucher's support for the "cap and trade" bill restricting carbon emissions, which was anathema in the area's coal-producing communities.

I'm tickled to death he's our President. Mark Matney on Donald Trump

For Mark Matney, a teacher in Abingdon who usually votes Republican but had sometimes supported Boucher, that was the breaking point.

"When people wanted something done and they went to Rick, he seemed to get it done. I mean, I've seen many families he helped," Matney told me. "Then when Obama come in, Rick helped author cap and trade. It was at that moment when it got bad. When he done that with cap and trade, it was like he wasn't representing his people anymore."

Boosted by heavy spending from outside conservative groups who linked Boucher to Obama and House Democratic leader Nancy Pelosi in a barrage of television advertising, Griffith, a Republican state House member, blew past the Democrat in 2010 by nearly 10,000 votes.

Boucher was hardly alone: The 2010 election virtually annihilated the center-right so-called "blue dog" Democratic House members, who mostly represented preponderantly white, heavily blue-collar, small-town and rural districts. Among those swept away that fall were Jim Oberstar in Minnesota (first elected in 1974), Gene Taylor from Mississippi (1989, in a special election), Ike Skelton of Missouri (1976), Earl Pomeroy of North Dakota (1992), Paul Kanjorski of Pennsylvania (1984), John Spratt of South Carolina (1982) and Chet Edwards of Texas (1990), as well as a long list of small-town Democrats who had won more recently.

Blake Andis used to be chairman of the Washington County Democratic Party. Now he's an official with the Washington County Republicans. See him in the video above.

Being traditional raised up here I always started out a meeting with the Pledge of Allegiance and a prayer and a couple of times I was asked not to pray. So, I thought, well, something's not right. Blake Andis

Jon Vogel, now a Democratic consultant, was executive director of the Democratic Congressional Campaign Committee during the GOP's 2010 sweep. He says it wasn't complacency that doomed the blue dog rural Democrats, it was that many voters who had long split their tickets between local Democrats and presidential Republicans were no longer willing to do so with Obama in the White House.

"I don't think anyone was caught napping," Vogel says. "All of those guys got ready and ran their campaigns, but you couldn't survive what was coming. You couldn't overcome the DNA of the district, no matter how good a campaign you ran."

Republicans have since solidified their hold over Boucher's old district. Griffith has carried at least three-fifths of the vote in each of his three re-elections. While Boucher and other Democrats view their 2018 nominee, farmer Anthony Flaccavento, as an energetic candidate, Griffith remains a strong favorite in part because of Trump's solid popularity here. Trump carried 68% of the vote in the 9th District in 2016 (the most in any Virginia US House district) and Matney says none of the personal and political controversies swirling around the President have dented his standing with conservatives here.

"To be 100% honest with you, no," he says. "They think that he's up there to do what we want him to do: protect our guns, protect our rights, less government, more jobs. That's all they see, and I'm tickled to death he's our President."

Trump's strong approval ratings among the white non-college and Christian voters who constitute a larger share of small-town and rural districts represent a huge headwind for Democrats in such places this fall. The party is targeting several Republicans in seats that fit that description, such as the northeast Iowa seat held by Rod Blum, the northern Maine seat held by Bruce Poliquin, John Faso's upstate New York seat and Rodney Davis' district in downstate Illinois.

Democratic tailwinds in the suburbs

Amanda Kelly had never been involved in politics. Frustration after 2016 has her working to defeat her Republican congresswoman.

I thought, 'No way, he's not going to win,' but when he did, I decided I had to start doing something because Congress is the only check. Amanda Kelly

But, by far, the Democrats' best opportunities are clustered in urban and suburban areas. In those places, Trump faces much lower approval ratings than usual for a Republican president among college-educated white voters, especially women. In the latest Quinnipiac University national poll, Trump's net disapproval rating among college-educated whites (19 points negative) was almost exactly as bad as Obama's among blue-collar whites in Pew Research Center polling (20 points negative) just before Republicans routed the small-town House Democrats in 2010.

With that tailwind, Democrats are pursuing Republican-held suburban seats in every region. In the East, they have multiple opportunities around New York City, Philadelphia, Miami and New Jersey; in Virginia, they have a strong shot not only at Comstock but also at Republican Rep. Dave Brat, who holds a seat centered on the Richmond suburbs that swung toward Democrats in last fall's gubernatorial and state House elections. In the Midwest, Democrats are targeting suburban Republican-held seats around Chicago; Minneapolis; Kansas City, Missouri; Des Moines, Iowa; and more distantly Omaha, Nebraska. In the far West, Democrats have good chances in suburban Republican-held seats around Los Angeles and nearby Orange County; Tucson, Arizona; Denver; San Antonio; and Seattle. Democrats are also seriously contesting seats in Sunbelt metro areas that have previously been considered safe for Republicans, including districts around Atlanta; Charlotte, North Carolina; Dallas; and Houston.

Mirror image of 2010

The Republican losses in white-collar House seats this year almost certainly won't match the Democratic retreat in blue-collar seats in 2010 because the GOP doesn't have quite as many members in seats that have moved away from the party at the presidential level. But the general dynamic, and direction, of change could prove very similar: The suburban Republicans in 2018, like the small-town Democrats in 2010, are standing on floorboards of support that have been rotting for years -- and may not be able to survive the added weight of hardening discontent with a President from their party.

Comstock's embattled situation in Virginia's 10th District captures that problem. First elected in 2014, Comstock won re-election in 2016 with 53% of the vote, although Clinton carried 52% there. With Trump in office, though, the district broke decisively last November for Democrat Ralph Northam over Republican Ed Gillespie in the governor's race and swept out several Republicans holding seats in the state House that overlapped with Comstock's seat.

The first general election public poll in the district, by Monmouth University, showed the Democratic nominee, state Sen. Jennifer Wexton, leading Comstock by an imposing 10 percentage points. A 53% majority of the district's voters said they disapproved of Trump's performance, and more than four-fifths of them said they intended to vote against Comstock.

"I think everybody is looking at her race and saying, 'How in the world does she win?' " says Sabato, the University of Virginia political scientist.

Like many suburban Republicans, Comstock is running in a diversifying district (Hispanics, Asians and minorities who classify themselves as "other" combine for about 32% of the population). Democrats are hoping for the same kind of strong turnout among them that helped Kathy Tran, a refugee from South Vietnam, win a House of Delegates seat last fall in a district that overlaps with Comstock's.

"I think that the energy that we really helped to start in 2017 is ... going (to) be a huge tsunami in November," said Tran, who became one of the first two Asian-American women in the state House. "My experience in Virginia has been that we have turned the corner and the vast majority of people want a welcoming and inclusive commonwealth."

Rep. Barbara Comstock speaks during a hearing on Capitol Hill.

Comstock, like the other suburban Republicans, also risks being caught in the backlash against Trump among many college-educated white voters, especially women. (In the Monmouth poll, 60% of the district's whites with a college degree disapproved of Trump's performance.) And she is confronting a surge of energy among liberal-leaning voters, even many of those who had not previously been politically active.

Amanda Kelly, a retail store manager from Bluemont, is one of those. She didn't vote until she was 30 (for Obama in 2008) and before the 2016 election couldn't name her governor or US representative. All that changed after Trump's victory.

"At the rallies I saw violence, I saw racism, assault, terrible things (and) I thought, 'No way, he's not going to win,' " she says. "But when he did, I decided I had to start doing something, because Congress is the only check."

Now Kelly has become a tireless activist in Indivisible, the grass-roots Democratic group committed to opposing Trump, as well as other local political organizations; in the 24 hours before I spoke with her last month, she had participated in two separate demonstrations (one that required her to arrive at 4 a.m. to start setting up) over Trump's family separation practice.

"People feel really passionate," she says. "You know, fortunately Trump provides a lot of fodder for that."

Over 300 miles away in the state's far southwest corner, Matney is just as passionate in his embrace of Trump and his determination to maintain the Republican congressional majority that supports and defends the President. If anything, Matney says, as a socially conservative Republican he feels more connected to Trump in office than he did as a candidate.

These clashing perspectives demonstrate why the midterm election is less likely to produce a wave that rolls equally across the country than a split-level current that carries metropolitan America closer to the Democrats without seriously breaching the Republican fortress beyond it. That could leave the Congress, and the country, glaring across demographic and geographic divides etched as sharply as during the most polarized times in American history.

"It means legislative gridlock," says Cole, the Republican representative from Oklahoma. "I always tell people I don't have a Democratic member of Congress who lives within 200 miles of me in any direction. These divisions don't start in Washington, DC, and come down; they are in the country and working up. ... We have been seeing this coming for a while. But we really are in an age of regionalization of politics that is reminiscent of the 1850s."