Analysis by Ronald Brownstein, CNN

(CNN) -- The first polling reactions to last week's summit between President Donald Trump and Russian President Vladimir Putin in Helsinki, Finland, should extinguish the last doubts, if any remained, that outrage over Trump's behavior is likely to ever dislodge a meaningful portion of his core supporters.

And that may encourage Democrats to take a second look at important new economic ideas from the centrist party group Third Way about how to reach the rural and blue-collar voters central to Trump's coalition. Their message is that Democrats are more likely to loosen Trump's grip on at least some of his supporters if the party stresses opportunity over outrage.

Each time Trump shatters previously accepted boundaries of presidential behavior, it's become a ritual for political strategists and analysts to ask whether this will be the moment that cracks the foundation of his support, particularly among his core groups of blue-collar, older, evangelical and rural whites.

But the reaction to the summit, like his defense of white nationalists in Charlottesville, the firing of then-FBI Director James Comey and the Stormy Daniels maelstrom, suggests that very few of those voters are willing to abandon the President because of questions about how he behaves.

That pattern persisted in polls over the weekend from ABC News/Washington Post and NBC News/Wall Street Journal finding responses to the summit largely divided Americans along the familiar lines of race, generation, education, partisanship and geography that have characterized the reaction to Trump's presidency from the outset. In the NBC/WSJ survey, conducted just before and after the summit, almost exactly three-fifths of whites without college degrees -- Trump's bedrock constituency -- still said they approved of his job performance.

Though the degree and frequency of Trump's provocations may be unique, many of his supporters appear to be making the same calculation voters have commonly applied to earlier presidents: So long as they believe he is fighting for their interests, they will overlook, or at least tolerate, behavior that troubles them -- from paying off porn stars to fawning over Putin.

One of the great debates among political observers is whether Trump's supporters are drawn to him primarily because they believe he is fighting for their racial and cultural interests or their economic needs. But it's become more and more apparent that question represents a false choice, because many of the voters who are most uneasy about the nation's social and demographic change are also concentrated in the places that are struggling to keep pace as the economy hurtles into the digital era.

Growth in businesses confined to fewer counties

The latest evidence of that dynamic comes from an important study by Third Way, a group that promotes centrist policies for Democrats. In a report released late last month, the group found that the formation of new businesses is increasingly concentrating in a smaller number of US counties, while about two-thirds of American counties have lost more businesses than they created in the past decade, according to census data.

"In essence, the digital age has created two different economies spread out through America," Jim Kessler, the group's senior vice president for policy, wrote in the study.

The gulf between the counties creating and losing businesses is expanding. Business formation was much more widely shared around the turn of the century: From 1995 through 2004, the group found, 2,200 counties added businesses and just 964 suffered net losses. But from 2005 through 2015, the group found, only 1,029 counties added businesses, while 2,109 lost them. The counties adding businesses also added 6.7 million private-sector jobs from 2005 to 2015, while the counties shedding businesses lost 1.2 million private-sector jobs. Annual wages in the places adding businesses were about 20 percent higher than in the losing counties. What's more, the losing places surrendered an even greater share of their businesses from 2005 to 2015 than they had in the previous 10 years.

While the counties adding businesses over the more recent decade included a number in energy-producing regions, the winners were mostly concentrated in major metropolitan areas. The very top of the list for net business creation included the counties encompassing Los Angeles; Brooklyn, New York; Houston, Miami; Austin, Texas; and Queens, New York. The counties topping the list for total job creation included those around Houston, Manhattan, Los Angeles, Santa Clara (Silicon Valley), Seattle, San Francisco, Austin, San Antonio and Dallas.

As the economic performances of these counties diverged, so too did their political preferences. In 2004, Republican George W. Bush beat Democrat John Kerry by a little over 1 percentage point in the counties that have gained new businesses and by about 3 points in the losers, a small difference overall. But in 2016, Trump beat Hillary Clinton by 6 percentage points, or about 3.5 million votes, in the counties losing businesses.

Clinton, in turn, beat Trump by over 9 percentage points, or around 6.4 million votes, in the counties adding new businesses. In the 100 counties adding the most new businesses, Clinton routed Trump by nearly 25 percentage points and over 9 million votes. Kerry's margin in those 100 counties was less than one-third as big. (To compare apples to apples, Third Way measured both the 2004 and 2016 presidential results in the counties that have gained or lost businesses over the 2005-to-2015 period.)

These dramatic contrasts reinforce the findings of the Brookings Metropolitan Policy Program. Its work has shown that although Clinton won fewer than one-sixth of America's counties, her counties accounted for about two-thirds of the gross domestic product and the job growth during the final years of Barack Obama's presidency.

All these analyses show how the Democratic Party is strengthening its position in thriving major metropolitan areas that are racially and religiously diverse, increasingly white-collar, deeply connected to global markets and leading the transition into the information-age economy. Republicans, in turn, are consolidating their hold on small-town and rural places that remain preponderantly white, mostly Christian, heavily blue-collar and more rooted in such dominant 20th-century industries as manufacturing, energy production and agriculture.

Divide worries both parties

As I've written before, neither party is entirely comfortable with that partitioning. Republicans fear the long-term implications of losing ground in the places that are gaining population and jobs and driving economic growth. That dynamic is vividly apparent in the midterm risks that are gathering for House Republicans who hold urban and suburban seats around New York, New Jersey, Philadelphia, Chicago, Minneapolis, Kansas City, Miami, Charlotte, Denver, Seattle, Los Angeles and potentially Atlanta, Dallas and Houston as well.

In a mirror image to the NBC/WSJ findings on Trump's solid approval among whites without college degrees, the survey released Sunday found that almost exactly three-fifths of whites with such degrees disapproved of his performance. That includes not only 65 percent of college-educated white women but also a 52 percent majority of college-educated white men, typically a very reliable Republican constituency.

In both their 2010 and 2014 congressional sweeps, exit polls found that Republicans won those college-educated white voters by at least 16 percentage points; but the NBC/Wall Street Journal poll now showed them preferring Democrats by 10 points for November. Given Trump's weakness among white-collar whites, Democrats likely have room to improve even more with those voters before November -- compounding the GOP's vulnerability in suburban seats.

But some Democrats worry that even a commanding position in thriving white-collar metro areas would leave them operating across too narrow a geographic base to consistently assemble majorities in the House, the Senate or the Electoral College. Even amid all the waves crashing around Trump, Democrats face huge barriers in small-town and working-class communities: In the NBC/WSJ poll, Republicans led in the race for Congress among rural voters by 26 percentage points and among whites without college degrees by 22 points (including a daunting 16-point advantage among non-college white women, who Democrats are hoping to pry away from the GOP this fall.)

Kessler said such results, like the shift in the presidential vote his study tracked, underscore why Democrats must find new ways to speak to voters beyond booming urban areas.

"We have an opportunity crisis," he says. "If you live in one-third of the country, it is not apparent; but if you live in two-thirds of the country, it is very apparent. Democrats do not represent those two-thirds of the country. It is apparent in how much our vote has slipped (in those places)."

Third Way has produced an agenda of ideas designed to disperse economic opportunity more widely; one of its centerpieces is an "American Innovation Bank" designed to encourage more small business lending and venture capital investment beyond the metropolitan centers where it is increasingly concentrating. (Firms in just California, Massachusetts and New York, the group pointedly notes, receive three-fourths of all US venture capital funding.) Other thoughtful groups, from the Revolution venture capital fund established by AOL founder Steve Case to the nonpartisan Economic Innovation Group, have also formulated proposals to encourage more business formation and job growth beyond a handful of superstar cities.

The question is whether any of these ideas are powerful enough to reverse the economic or political currents separating metropolitan and non-metro America in the Trump era. The tendency of talent and capital to cluster in a relatively few hotbeds of innovation has proved to be a cornerstone of the digital economy. And it's deeply unclear whether even a stronger Democratic economic agenda aimed at the places those changes have left behind would overcome the strong affinity so many voters in them feel for Trump's confrontational cultural and racial messages.

On both the political and economic fronts, Kessler argues, Democrats must try to bridge these divides. "If we don't try, then the outcome is going to be more of this bifurcation," he says.

That's good advice. But no one should doubt the difficulty of reversing the accelerating economic, cultural, demographic and political separation between the blue-leaning major metropolitan areas and the reliably Republican exurban, small town and rural communities beyond them. If someone were to chart a modern equivalent to the Mason-Dixon line that once demarcated America's fundamental divide (then between the North and South), it would probably look like one of the beltways that divide many metropolitan areas between a bustling urban core and the smaller places beyond.