Republican presidential hopeful businessman Donald Trump fields questions at The Family Leadership Summit in Ames, Iowa. Scott Olson AFP/Getty

In America this summer, the seams are showing.

Against the backdrop of the accelerating presidential race, the strains of adapting to the nation’s hurtling demographic and cultural change are growing increasingly visible. For all of the economic anxieties many Americans still express, the most polarizing conflicts this year are dividing the nation along lines of race, ethnicity, and culture, not class. The most urgent question in 2016 may be how we live together in a relentlessly diversifying society that, in many respects, looks to be retreating to separate corners.

That challenge is framed most viscerally by Donald Trump’s rise in the Republican presidential race. Often to the discomfort of GOP leaders, Trump’s ascent has illuminated how much of their party’s base is deeply uneasy about immigration and, more broadly, the country’s ongoing demographic change.

Trump has embraced hard-line immigration positions that few mainstream party leaders have previously endorsed: physically deporting the estimated 11 million undocumented immigrants, ending birthright citizenship, and even criticizing the public speaking of Spanish. Yet polls in recent years have found a significant constituency for all those ideas among Republicans, especially those without a four-year college degree.

In an NBC/Wall Street Journal poll in July, for instance, 52 percent of noncollege Republicans (compared with 32 percent of Republicans with degrees) said all undocumented immigrants should be deported. In a 2011 Pew Research Center survey, about half of both noncollege- and college-educated Republicans said they would revoke birthright citizenship. And in 2012, Pew found that three-fifths of noncollege Republicans (and two-fifths of those with degrees) said it bothered them when they came in contact with immigrants who speak little English. More fundamentally, a Public Religion Research Institute survey in June found that a majority of noncollege Republicans (again joined by about two-fifths of those with degrees) believes “the growing number of newcomers from other countries threatens traditional American values and customs.”

All of these results show that, to borrow from Billy Joel, Trump didn’t start this fire; he has simply fanned the embers that were already smoldering in the GOP coalition. And now that this flame is burning, it’s not clear how GOP leaders can extinguish it, though they fear its long-term electoral implications. Even if Trump falters, the sentiments he has stirred are likely to inspire a platform fight over immigration at next summer’s GOP convention—and redouble Republican congressional resistance to comprehensive immigration reform in 2017 no matter which party wins the White House. By demonstrating how many Republican voters respond to a deeply insular, even nativist, message, Trump may have seeded heightened conflicts over immigration that will long outlive his political career.

Simultaneously, the tensions between black leaders and law enforcement are loosening a second stitch. The grassroots movement that has emerged since 2014 to challenge how the criminal-justice system treats African-Americans is increasingly attracting a conservative backlash that several of the GOP presidential contenders are now actively fanning. Rising murder totals in many major cities, several high-profile shootings of police officers, and the massacre of African-American worshippers in a Charleston, South Carolina, church have heightened tensions across this racial and ideological divide.

These volatile ingredients are reconfiguring the political landscape around the Black Lives Matter movement. So far, the movement’s leaders have focused more on challenging than on persuading white America—a strategy symbolized by its repeated disruption of Democratic campaign events. But the growing conservative effort to portray the movement as a threat to law enforcement—and by extension, middle-class safety—shows the risks of failing to build a transracial consensus for change.

In the coming years, the United States will grow increasingly reliant on workers from minority groups, as the number of working-age whites is projected to decline. This means not only African-Americans, but all Americans, would benefit from ensuring that fewer black lives are lost to mass incarceration or unequal policing. Yet the early volleys from the 2016 GOP contenders signal that the Black Lives Matter movement could become politically isolated—and provoke further white alienation from Democrats—if activists can’t define reform in an inclusive way that values both equal treatment and personal responsibility.

Kim Davis, the Kentucky county clerk who claims her religious beliefs exempt her from upholding the Supreme Court decision legalizing same-sex marriage, is pulling at a third fragile thread. The Court decision seemed to consecrate a broader cultural acceptance of gay relationships. Instead, Davis’s defiance—and its quick embrace by several GOP contenders—has signaled that a hard slog through sustained resistance probably awaits each further step toward equal treatment for gays, such as for workplace protection.

Each of these disputes—immigration, relations between African-Americans and the criminal-justice system, same-sex equality—align most Democrats with the forces of change and most Republicans with the resisters. On most key questions, public opinion is flowing toward the acceptance of demographic and cultural transition, as it usually has in American history. But today, the balance remains precarious between those who would embrace or reverse these changes. That tenuous balance could decide a presidential campaign that seems destined to tear at the nation’s most fragile connections.

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