Donald Trump delivers a speech during the Republican National Convention in Cleveland on Thursday. (Alex Wong/Getty Images)

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THESE ARE anxious times in America. Despite a steadily, if slowly, growing economy and the absence of a major war, people remain troubled by a sense of national underperformance and myriad social ills, most recently the surge in racially tinged fatal shootings committed by law enforcement officers and against them. A new Gallup poll reports that only 17 percent of Americans feel satisfied with the way things are going, the lowest percentage since October 2013 — and down 12 points in just the past month.

For many, of course, a cause of concern is Donald Trump, who accepted the Republican presidential nomination Thursday evening. Belligerent and erratic, Mr. Trump nevertheless has a serious chance to win in November. In his acceptance speech, he sought to enhance his political prospects the only way he knows how: by inflaming public angst, so as to exploit it.

Mr. Trump took real challenges and recast them in terms that were not only exaggerated but also apocalyptic. “The attacks on our police, and the terrorism in our cities, threaten our very way of life,” he claimed. Though he addressed issues ranging from public safety, to immigration, to trade, Mr. Trump’s proposed solutions all shared a common premise: the way to overcome difficulty is through force. To American companies that exercise their right to move production abroad, the Trump administration will administer unspecified “consequences.” A giant wall will block migrants and drug traffickers along the Mexico border. And “law and order” — an old trope of Richard Nixon and George Wallace that Mr. Trump brought out of retirement — will be restored.

Perhaps politically effective because of their simplicity, Mr. Trump’s now-familiar formulations would fail as actual policies — because they are simplistic. There is no practical prospect, for example, of constructing the wall he insistently touts; even if built, drug traffickers and others could eventually tunnel under it. And, as per usual, last night he added no details to this plan that might convince anyone otherwise.

As for law and order, the president has at most indirect influence over thousands of law enforcement agencies across the country. To the extent it can be taken seriously at all, Mr. Trump’s assertion that “safety will be restored” on the day of his inauguration implies a vast federalization of a traditional state and local function, contrary to long-standing law and custom — not to mention the small-government doctrine of the Republican Party that has so unwisely and hypocritically hitched its wagon to Mr. Trump’s star. To tense communities in need of the nuanced toughness that police chiefs such as David O. Brown of Dallas have successfully applied, a President Trump would project from the White House a repressive attitude, unbuffered by a shred of sensitivity, racial or otherwise. Less safety, not more, could be the result.

Mr. Trump began his speech by presenting himself as the bearer of painful but necessary truth. And no doubt, for many of his listeners, his words expressed a deeply felt emotional reality. There is real fear in the land; real pain. But it will take real leadership, not the wishful, demagogic brand Mr. Trump embodied Thursday night, to address this.