It seems the notion of the Republican Party being a white nationalist party is picking up currency among the punditocracy. Over at Vox (boldface mine):
You don’t see working-class Latinos and African Americans rallying to Trump’s standard, even though economic conditions are worse for nonwhites than for whites. And Trump is surging in 2015 even though today’s economy is much stronger than the economy of 2012 or 2008.
A more plausible theory is to apply Occam’s razor: A substantial minority of white Americans are rallying behind Trump’s white ethnocentric agenda because they are — reasonably — concerned that ongoing demographic changes are threatening white people’s political power in the United States…
…whatever economic troubles middle-class white Americans have suffered over the past generation pale in comparison to the struggles of black and Latino Americans, who have lower incomes and far less wealth. A political movement that primarily resonated with people seized by economic anxiety would have a very different look than Trump’s…
It’s of course possible that @Non_PC_guy is confused, and actually only thinks he cares about the browning of America and the Islamization of the Occident because of things liberals think are wrong with the American economy. But it’s also true that 2015 marks the first time in American history that white Christians are no longer a majority of the population.
America has a black president, and he has presided over the most diverse set of executive branch appointments in history and the most diverse federal judiciary in American history. The share of the population that was born in a foreign country has reached a level not seen in generations, and even many liberals (including Barack Obama!) are expressing profound anxiety that the youngest cohort of Americans are using their clout to impose a freedom-ravishing regime of “political correctness” on the country.
These are profound demographic changes, and they have real consequences. The weight of Hispanic voters in the Democratic Party coalition is a key reason that backing a “path to citizenship” for undocumented immigrants has become a core item on the Democratic Party policy agenda. And the weight of African-American voters in the Democratic Party coalition is a key reason that Democrats are becoming much more attentive to complaints about the ways African Americans are treated in the criminal justice system. Whether you like these changes or not, they are unquestionably real and significant, and it’s natural that attentive citizens would form opinions about their merits and that some people would end up on the “these changes are bad” side of the argument.
Meanwhile over at Slate (boldface mine):
But there’s another possibility that challenges this sense that Trump feeds—and feeds off of—false consciousness. What if Trump’s racism attracts supporters? What if his bigotry is the point?
With the end of the 1960s and the rise of black electoral power, explicit racism fell out of political favor. It never disappeared—as late as the 1990s, prominent candidates were race-baiting their opponents—but it diminished, replaced by an era of “dog whistle politics” where politicians played on implicit bias with codewords and innuendo. Richard Nixon had “law and order”; Ronald Reagan had “welfare queens”; and in a move toward the explicit, George H.W. Bush had “Willie Horton” and an ad campaign that tied crime together with primal racial fears in a devastating hit on Michael Dukakis. “No campaign ever turns on one issue,” observed historian Dan T. Carter, “but no one—no one—who followed the  campaign believes George Bush had any more devastating ally than the homicidal black rapist Willie Horton.”
…What’s key is that there’s always been a portion of voters who are activated by racist appeals. And in an erstwhile herrenvolk democracy, this shouldn’t be a surprise. They show up in surveys, polling, and research data as Americans who rank high on racial resentment or hold strong anti-black views. They respond favorably to racial demagoguery—whether from candidates or media or both—and exist throughout American politics, in the far-right margins as well as a voting group in the Republican Party.
In fact, their racism makes them more partisan; in a 2010 paper, political scientists Michael Tesler and David Sears found that for Republicans in the era of Obama, the higher their racial resentment, the stronger their attachment to the GOP…
Economic anxiety plays a part here. But maybe Trump has discovered something we all like to deny: That in the 21st century, the racist vote is larger, louder, and more influential than we ever thought.
First, as I’ve noted before (that is, in 2008), this loss of cultural status, of being primus inter pares, is a major motivation for what I’ve called the Palinist right. For them, politics primarily exists to enable the social restoration of ‘real’ Americans and the emotional and social advantages that restoration would provide to its followers.
Second, the Republican Party, ever since it adopted the Southern Strategy, has made racists an essential part of its governing coalition. That is not to say that most Republicans are racists (or that no Democrats are racist), but to note the obvious: Republicans can’t win without racist whites.
I don’t know whether or not it’s a good thing, but Trump’s overt bigotry has forced the chattering class to confront what we Dirty Fucking Hippies knew all along. Probably should have listened to us sooner…