By Ronald Brownstein

(CNN) -- The overwhelming defiance in the NFL on Sunday to President Donald Trump's attacks on protesting players encapsulates the high stakes for the GOP in his belligerent approach to race relations.

Like the earlier exodus of business leaders from Trump's advisory councils after his widely criticized response to the Charlottesville, Virginia, violence, the decision by not only players but also coaches and wealthy owners to literally lock arms in defiance of the President illuminates how even those who agree with other aspects of Trump's agenda increasingly find his views on race too toxic to associate with.

From the first day of Trump's presidential campaign in 2015 -- when he denounced Mexican immigrants as "rapists" and "criminals" -- Trump has targeted the groups in the electorate who polls show feel the most threatened by demographic, cultural and economic change, particularly older, blue collar, evangelical and non-urban whites.

He has systematically encouraged these voters to think of themselves as a group under siege -- and to view him as the champion who will defend "our heritage," as he put it in the speech Friday night when he targeted the NFL protesters before a virtually all-white audience in Alabama.

This polarizing approach has produced some undeniable near-term political benefits for Trump. In 2016, he amassed a larger margin among whites without a college education than any candidate since Ronald Reagan in his 1984 landslide. Reflecting his dominance of rural and small-town America, Trump also won more counties than any candidate since Reagan that year.

In this cultural and racial crucible, Trump has also forged a passionate connection with his core supporters that have survived his presidency's extraordinarily turbulent first months. Many conservative analysts have welcomed the latest confrontation-which has spilled out beyond the NFL to encompass Steph Curry and the Golden State Warriors of the NBA -- because they believe it positions Trump as defending the traditional values of flag and country that his supporters fear are in retreat.

"In the long term, this is going to be toxic for the GOP"

But through his belligerence on these issues, Trump also risks stamping the GOP as a party of racial intolerance precisely as the millennial generation, the most diverse generation in American history, is passing the predominantly white baby boom as the largest generation of eligible voters; the post-millennial generation that will enter the electorate behind them starting in 2020 is even more diverse.

"In many ways, Trump appears to be a man out of time," says Daniel Cox, research director for the non-partisan Public Religion Research Institute, which polls extensively on cultural attitudes. "His ideas about masculinity -- that it's all about being tough, never apologizing -- his views about gender roles, and race are anachronistic. ...The longer he's in office, the longer he refuses to modulate his tone, or soften his views the more he is going to appear being completely out of touch to millennials who are going to start wielding tremendous political power."

As demonstrated by the widespread resignations from his business advisory councils after Charlottesville and the participation of NFL owners in Sunday's pushback, Trump's approach is also straining the GOP's traditional hold on college-educated white voters, many of whom lean center-right on economics and government spending, but center-left on cultural and racial issues.

In the most recent CNN poll, almost exactly two-thirds of both millennials and college-educated whites said they disapproved of Trump's handling of race relations. Over three-fourths of minorities also disapproved. In a Pew Research Center survey in August, three-fifths of both college-educated whites and non-whites and fully two-thirds of adults younger than 30 said they considered Trump prejudiced.

As Republican pollster Kristen Soltis Anderson, who has extensively studied the millennial generation told me after Charlottesville, "I wouldn't blame a young person who is just becoming interested in politics who thinks the GOP ... is comfortable with white supremacists. Not just because of perceptions of what Trump believes, but because of the accurate perception that a majority of Republican voters stand with him, even on his most controversial views."

Republicans, as Cox notes, now possess several structural advantages that may initially muffle the impact of that verdict, from lower turnout among young people, to excessive concentration of Democratic voters in large urban areas, to gerrymandering of congressional districts. But, he adds, "in the long term, this is going to be toxic for the GOP."

Whit Ayres, a Republican pollster who has argued the party needs to expand its appeal to growing minority groups, also worries that Trump's persistent racial confrontations are narrowing the party's reach-even as it mobilizes his core supporters. "This is all part of Trump's consistent pattern of solidifying and energizing the 40% of Americans who are with him by attacking the 60% who are not," Ayres said in an e-mail. "That may be a good strategy to energize his supporters, but it makes it exceedingly difficult to accomplish anything when a large majority of Americans solidly oppose him and his agenda."

Racial tensions in a majority-minority nation

Whatever the long-term partisan implications of Trump's confrontational approach to race, the near-term consequence for the nation is an unequivocal rise in racial tension. The US today is experiencing the most profound demographic change since the turn of the 20th century, with minorities already comprising a majority of all students in the K-12 public school system nationwide; demographers project that as soon as 2020 kids of color will comprise a majority of all Americans under 18. White Christians, who represented a majority of Americans for most of our history, fell below 50% of the population sometime around Barack Obama's reelection in 2012. And the share of the US population that is foreign-born is on track to reach its highest level ever by around 2025, the Pew Research Center projects.

Change of that magnitude has always produced friction, and the impact is magnified today because it is coming even as millions of Americans, particularly those without advanced education, have faced years of stagnating or slowly growing incomes.

So any president today would face the challenge of holding together a society strained by these pressures. But Trump is bringing gasoline, not water, to these smoldering conflicts.

Through his sharp-edged message and agenda, Trump is systematically widening the central fault line in American politics and life: the fissure between those who are largely optimistic about the profound social and economic changes reconfiguring American life, and those who feel most uneasy about them.

Trump has stirred passionate support from what I've called the GOP's "coalition of restoration," centered on the older, blue-collar, evangelical and non-urban whites most uneasy about the ways America is changing. In turn he has provoked intense opposition from the Democrats' heavily urbanized "coalition of transformation" revolving around minorities, millennials, and college-educated whites who largely are comfortable with both demographic and economic change.

An impossible mission of restoration

Trump has firmly planted the GOP on the side of those resisting all of these changes. But Trump's promise to reverse the change -- the inherent message of his pledge to "make America great again'-is a promise that no president can keep. No matter how many immigrants he deports, or black protesters he disparages, the nation will inevitably grow more diverse; likewise, no matter how many trade deals he scuttles, the impact of global competition is likely to only increase.

By pointing his coalition toward an impossible mission of restoration, he is squandering the opportunity to help Americans recognize their shared interests in this period of unsettling change. Ultimately, the older white Americans central to Trump's coalition need more of heavily diverse younger America to succeed-because those are the future workers who will bear the payroll taxes that support their Social Security and Medicare. To improve economic growth, the nation likewise needs to bolster the places that have been hurt by international competition without extinguishing the export opportunities powering prosperity in the big cities that are increasingly selling not only products but also advanced services to the world. And rather than viewing immigration as a threat to native-born workers, Trump could join the communities across the Rust Belt that now consider it a "demographic lifeline" to help reverse population loss and economic decline.

In the 1950s, Senator Joe McCarthy's crusade to root out (usually imaginary) Communists finally crashed when he pushed too far against the Army. In targeting the NFL, Trump similarly may have broken his lance against a foil too powerful for him to intimidate with his racial barbs. From his refusal to immediately condemn David Duke during the 2016 GOP primaries, to his attacks on a US born Mexican-American judge, to his "some very fine people" defense of neo-Nazis and Ku Klux Klan marchers in Charlottesville and his pardon of former Arizona sheriff Joe Arpaio, Trump has appealed to white racial resentments more overtly than any political leader in either party since George Wallace. The price is high, but from business leaders to professional sports leagues, Trump is systematically compelling every institution in American society to decide whether it can afford to stand beside that acrid flame.