THERE is a moment in “The Plot Against America”, Philip Roth’s tale of America succumbing to 1930s-style authoritarianism, when the nine-year-old protagonist experiences a profound revulsion at the foibles on which wickedness thrives. “Never in my life had I so harshly judged any adult,” he recalls of his Jewish aunt’s preening over a brief interaction with the anti-Semitic president, Charles Lindbergh. “Nor had I understood till then how the shameless vanity of utter fools can so strongly determine the fate of others.” That is as much respite as the recently deceased author, who combined a stubborn faith in America with a gloomy view of its politics, allows his reader. There is no chance of America sharing his awakening. The power of the boy’s epiphany lies not only in its clarity, but also in its futility.

Roth’s pessimism about the prospect of national redemption should be instructive to critics of President Donald Trump’s policy of caging migrant children in isolation from their parents. They hope voters will recoil from both this ill-fated debasement of American values and its architect. But not even the policy’s cancellation on June 20th will achieve that. Though America has experienced many moral corrections, from abolitionism to the civil-rights movement, they have never come in the emetic moment Mr Trump’s critics pine for. The tortured issues of race and national identity that explain its dark times, as they do now, are too contested. America’s moral shortcomings under Mr Trump, including his attempted Muslim ban, slashing of the refugee programme and draconian border policy, were the promises of his election campaign. There are indeed too many echoes of 2016 in this latest row for his opponents to feel triumphant.

Mr Trump entered American politics, three years ago this month, with a campaign-defining rant against Mexican “rapists” and other illegal immigrants. It was reprehensible and effective in several ways. It positioned him with voters, most of them Republicans, who worried about immigration, and against the party’s patrician leaders, including his main rivals at that time, the Bush clan. It also showed, notwithstanding legitimate worries about the effect of immigration on wages, how well he understood the issue’s ability to connect with the racial anxiety of America’s dwindling white majority. He thereby engineered the most racially divisive election in years. Many Republicans disliked it. Yet because the Democrats are associated with the immigrant communities Mr Trump attacked, his tactic also turbocharged partisan enmity, which helped mollify them. In the run-up to what are expected to be gruelling mid-terms for Republicans, Mr Trump’s family separations were an effort to dust off a winning script.

There are many clues to that, starting with the erratic ways the administration defended it. Restrictionists such as Jeff Sessions, the attorney-general, presented family separation as a deterrent against illegal crossings. Kirstjen Nielsen, the secretary of homeland security, said it was not the administration’s policy. Mr Trump said it was because of a law passed by the Democrats, which is pretty much his 2016 strategy. The conservative media, now as then, tried to normalise his latest transgression with snarky jokes about what a no-big-deal it was and yet how crazy it made liberals. On Fox News, Laura Ingraham described Mr Trump’s strip-lit child cages as “essentially summer camps”. The president’s roster of outraged critics was also the same. It consisted of Democrats, pro-immigrant groups, Hollywood celebrities and Never Trump Republicans (including Laura Bush, whose intervention was not the game-changer her admirers hoped).

With only a small majority of Republican voters in favour of the policy, it had long looked like a misstep nonetheless. Yet Mr Trump’s decision to change course represents neither a disastrous retreat nor a major moral repulse. Indeed, the farrago signalled his strength as well as his weakness. Though prominent Trump supporters were unhappy with the policy, including some evangelical Christians, few blamed him for it. Franklin Graham called it “disgraceful”, but blamed “politicians for the last 20, 30 years”. Republicans in Congress, while working to find a legislative climbdown for the president, similarly restrained themselves. The policy’s cancellation by executive decree looks more like a precautionary step by a president enjoying his best ratings since his inauguration. There may even be a modest upside for him. The row provides Republicans facing difficult mid-term contests—including Senator Ted Cruz, who tried to provide a legislative escape route—with a rare issue on which they can claim to have disagreed slightly with the president.

Mr Trump’s opponents need to tread carefully. If politics were about being right, not winning arguments, Mr Trump would not be president. Most Americans want migrants to be treated humanely but, as his election showed, they also want strong borders. The ever-sprung trap Mr Trump sets his opponents is that, in feverish concern for the first, they neglect the second.

A dish best served cold

The danger for Mr Trump’s Republican supporters is less immediate, but greater and perhaps insurmountable. The history of America’s moral corrections suggests that what they lack in spontaneity they make up for with momentum. Democrats’ opposition to the civil war cost them the presidency for over two decades. Republicans’ opposition to civil rights cost them most of their non-white support, leading them to the white-identity politics from which Mr Trump is now wringing the last drop of juice.

It would be a short-term strategy, in an increasingly non-white America, even if he were a more ruthless demagogue than he is. Asked to compare Mr Trump with his fictional villain, Roth said Lindbergh was imposing, a heroic aviator, and Mr Trump “just a con artist”. His dog-whistle on immigration may sustain his presidency; it will not interrupt how America is changing. That combination spells a long-term disaster for his party.