In the sixteen months since he declared his candidacy, Donald Trump’s Presidential campaign has elicited comparisons to those of George Wallace and Barry Goldwater, to the hallucinatory paranoia of Joseph McCarthy, to the fascist preoccupations of Charles Lindbergh, and to lesser lights of American demagoguery like Father Coughlin and the Know-Nothings of the nineteenth century.

The unifying theme among these figures, beyond their disdain for democracy, was their common residence in the loser’s aisle of American history. McCarthy’s conspiratorial manipulation of the public eventually earned him the enmity of both Republicans and Democrats and a vote in the Senate to censure him. Wallace carried just five states and garnered thirteen per cent of the popular vote. Goldwater lost to Lyndon Johnson by sixteen million popular votes, winning just fifty-two Electoral College votes to Johnson’s four hundred and eighty-six. Richard Hofstadter’s 1964 classic “The Paranoid Style in American Politics” charted the lunatic genealogy of fringe movements dating back to the early years of the Republic, but the more sanguine assessment of that lineage is that few of these movements—anti-Catholicism, anti-Freemasonry, or Know-Nothingism, for instance—managed to sustain themselves in the long term or to fully inhabit the political mainstream.

Goldwater is heralded as the father of modern conservatism, but he could occupy that niche only because successive generations of his heirs refined and streamlined his message, buffing away the elements that the public saw as extremist. The modern Republican Party staked its claim on conservatism, not on Goldwaterism.

All this points to yet another reason why Trump represents a unique danger in American politics. Trumpism does not seek simply to make a point and pass on its genes to more politically palatable heirs, nor is it readily apparent why he would need to settle for this. When George Will announced his departure from the G.O.P., last summer, he offered a modified version of Ronald Reagan’s quote about leaving the Democrats—“I didn’t leave the Party; the Party left me.” But a kind of converse narrative applies to Trump; he didn’t join the Republican Party so much as its most febrile elements joined him. Trump is partly a product of forces that the G.O.P. created by pandering to a base whose dilated pupils the Party mistook for gullibility, not abject, irrational fear that would send those voters scurrying to the nearest authoritarian savior they could find. The error was in thinking that this populace, mainlining Glenn Beck and Alex Jones theories and pondering how the Minutemen would have fought Sharia law, could be controlled. (For evidence to the contrary, the Party needed look no further than the premature political demise of Eric Cantor.) The old adage warns that one should beware of puppets that begin pulling their own strings. ...