The U.S. has periodically witnessed political fads where nativist movements have burst onto the scene, gained some measure of popularity, and then flamed out. Trump's success to date in the Republican pre-nominating process is sort of a 21st century variation of the mid-19th century's rise and subsequent fall of the Native American Party aka the Know-Nothing Party.
Nativisim is a superficial ideology that serves no practical purpose. It does nothing but blame others for the nation's problems and is nothing more than a call for demographic balkanization.
Its sparks were evident in Pat Buchanan's failed candidacies of 1992, 1996, and 2000. In the wake of the Great Recession, it gained traction in 2010, and is currently poisoning the Republican Party and U.S. conservative movement. The combination of the aftermath of a severe recession, ongoing demographic change, unusually weak leaders, and populist pundits all fueled its rise. The Know-Nothing movement coincidentally emerged as the 1837-43 Depression was ending.
That Trump and his 21st century nativist movement is being coddled by the GOP leadership and fanned by populist radio hosts who masquerade as conservatives while spouting messages that run counter to the conservatism of an Edmund Burke, William Buckley, or Ronald Reagan does not confer upon it a sense of legitimacy. It is the antithesis of the American founding principles, a perversion of traditional conservatism, and a rejection of the U.S. constitutional republic.
Trump and his followers may be loud, but for all the noise they are currently generating, they very likely do not represent a desire to promote the best interests of the nation. Indeed, drawing from one of conservatism's foremost thinkers, Edmund Burke described that kind of situation in observing, "It is a general popular error to suppose the loudest complainers for the public to be the most anxious for its welfare." Burke understood that even as radical or reactionary movements championed the cause of the people, such rhetoric was little more than a means to far more sinister ends.
All said, just as was the case with the Know-Nothing movement, Trump and the nativists who are fueling his rise and poisoning the Republican Party and conservative movement will meet failure. They will fail, because they offer nothing of substance for addressing the nation's challenges (including the immigration-related issues that they have exploited in their rhetoric) or seizing its opportunities (pessimism, fear, and fatalism crowd out the pursuit of opportunity). The 21st century Know-Nothings will be repudiated in the general election, if by some chance Trump emerges as the Republican nominee (very unlikely). Afterward, over time, they will recede from the electorate and the Trump boomlet will vanish from nation's political landscape leaving behind only an historical footnote.