... Right-wing nationalist populism is nothing new in America; the genealogical lines of Trump and his immediate antecedents, Sarah Palin and the tea party, trace back at least to the later years of the Great Depression, when the demagogic and anti-Semitic radio priest Father Charles Coughlin turned against the New Deal and vilified Jewish “money changers” masterminding an international conspiracy to plunder his working-class flock. The movement was rebooted with a vengeance once the civil-rights revolution took hold in the 1960s: The term “backlash” grew out of the economic columnist Eliot Janeway’s 1963 observation that white blue-collar workers might “lash back” at new black competitors entering a contracting job market. That anger coursed through the quixotic presidential campaigns of the onetime Nixon aide Pat Buchanan from 1992 to 2000, through Ross Perot’s in 1992, and, most especially, through the four presidential runs of the segregationist Alabama governor George Wallace between 1964 and 1976.

What these campaigns had in common besides a similar core of grievances is that the candidates failed to win national elections. And they lost no matter what banner they ran under; like Trump, they and their voters variously identified as Democrats, Republicans, and Independents. But Trump’s unexpected triumph in 2016, claiming the Oval Office for unabashedly nationalist right-wing populism, changed history’s trajectory. His capture of the presidency and a major political party makes it highly unlikely that his adherents will now follow the pattern of their dejected forebears, who retreated to lick their wounds and regroup in the shadows after their electoral defeats.

When Jeff Flake, the self-styled Barry Goldwater conservative from Arizona, announced he was fleeing the Senate, he told Jake Tapper of CNN, “I think that this fever will break.” If only. At each defeat in the pre-Trump history of Trumpism, the rest of the country comforted itself by concluding that this troublesome minority had been vanquished. But these radicals are not some aberrational fringe. The swath of America that has now been reinvigorated and empowered by landing a tribune in the White House for the first time is a permanent mass movement that has remained stable in size and fixed in its beliefs for more than half a century. How large a mass? At the high end, Trumpists amount to the third or so of the country that has never wavered in support of the Trump presidency. A low-end estimate might bottom out at the quarter of the nation that still approved of Trump’s hero Nixon even when he surrendered the presidency rather than face near-certain conviction in an impeachment trial. ...