... Politically, Trumpism’s antecedents may be found in the presidential campaigns of Ross Perot and Patrick Buchanan for president in 1992 and 1996. Stylistically, the Trump campaign of early 2016 recalled the turbulence and rough rhetoric of George Wallace’s campaign rallies in 1968. Ideologically, Trumpism bears a striking resemblance to the anti-interventionist, anti-globalist, immigration-restrictionist, and “America First” worldview propounded by various paleoconservatives during the 1990s and ever since. It is no accident that Buchanan, for example, is thrilled by Trump’s candidacy.

But instead of focusing its anger exclusively on leftwing elites, as conservative populism in its Reaganite variant has done, the Trumpist brand of populism is simultaneously assailing rightwing elites, including the Buckley–Reagan conservative intellectual movement described earlier. In particular, Trumpism is deliberately and dramatically breaking with the proactive, conservative internationalism of the Cold War era and with the pro–free trade, supply-side economics ideology that Reagan embraced and that has dominated Republican Party policymaking since 1980. It thus poses not just a factional challenge to the Republican political establishment but an ideological challenge to the separate and distinct conservative establishment, long headquartered at Buckley’s National Review....

... As the debate has proceeded, many conservative intellectuals have attempted to accommodate what they see as the valid grievances expressed by Trump’s supporters. According to the libertarian social scientist Charles Murray, “the central truth of Trumpism” is that “the entire American working class has legitimate reasons to be angry at the ruling class.” Conservative intellectuals in general now seem inclined to agree.

But the problem for conservatives goes much deeper than expressing sympathy for the grievances of the aggrieved. If Trumpism were simply a cri de coeur of a sector of the population that feels left behind economically, it would seem possible for conservative power brokers in Congress and the think tanks to hammer out legislation that would begin to address the sources of anxiety. If the Republicans should capture the White House in 2016, one can envisage “deals” on Capitol Hill to strengthen border controls, reduce current levels of immigration, and reform the tax code in ways that benefit the middle and lower sections of the income ladder. One can also imagine legislation designed to stimulate economic growth and thereby assuage the pain of the Trumpist working class.

Two obstacles, however, stand in the path of such an accommodation. The first is that the contest between Trumpism and its conservative critics has become not just a dispute over details of public policy but an all-out war of ideas, one not easily papered over by pragmatic compromise. To many of its conservative critics, Trumpism is little more than a mishmash of protectionist, nativist, and (in foreign policy) neo-isolationist impulses. To the Trumpists, conservative internationalism is a rusty relic of a bygone era, and supply-side economics (with its corollaries of free trade, open border, and uncapped immigration) is an ossified dogma whose real-world consequences have been catastrophic for globalization’s “losers.”

For many years, during the Reagan era and beyond, the leading exponent of supply-side economics in Washington was the late Representative Jack Kemp. Today Kemp’s chief political disciple (who in fact worked for him as a speechwriter) is the Speaker of the House, Paul Ryan, a man who shows no sign of moderating his Kempian worldview. Nor does the editorial page of The Wall Street Journal—the ideological citadel of supply-side economics—appear to be yielding to the Trumpian barrage. It is not easy to see how—at the level of high principle and rhetorical advocacy—Kempism and Trumpism can be reconciled, either before or after the 2016 election.

In short, Trumpist populism is defiantly challenging the fundamental tenets and perspectives of every component of the post–1945 conservative coalition described in this essay. In its perspective on free trade, Trumpism deviates sharply from the limited-government, pro–free market philosophy of the libertarians and classical liberals. Despite some ritualistic support for the right to life and religious freedom, Trumpism has shown relatively little interest in the religious, moral, and cultural concerns of the traditionalist and social conservatives. In foreign policy it has harshly criticized the conservative internationalism grounded in the Cold War, as well as the post–Cold War “hard Wilsonianism” and distrust of Putinist Russia espoused by many national security hawks and neoconservatives. What Trumpism has addressed, loudly and insistently, is the insecurity and disorientation that large numbers of conservatives now feel about conditions at home and abroad. Whether this will be enough to unite the coalition at the polls (and beyond) remains to be seen....