PRESIDENT DONALD Trump has often likened the American experience of the covid-19 pandemic to a war. In many ways, the public-health battle against the coronavirus has resembled a military one. Health-care workers, like soldiers on the front lines, are sacrificing their lives. Firms are repurposing their factories to produce masks, ventilators and other life-saving gear. Families are rationing food and supplies.

But even as Americans come together to confront a common foe, they have yet to unite behind their commander-in-chief. Polls show that Mr Trump’s approval rating has increased by only a couple of percentage points since March 11th, the day the World Health Organisation declared the virus a pandemic. This compares poorly with other world leaders. According to data from Morning Consult, a pollster, Emmanuel Macron’s approval has jumped by eight percentage points in the same period; Boris Johnson’s has surged by 14 points; Justin Trudeau’s by a whopping 18 points. Of the eight world leaders in Morning Consult’s sample, only Abe Shinzo of Japan and Jair Bolsonaro of Brazil have fared worse.

Judged against his predecessors, Mr Trump also underperforms. A look at five national emergencies, spanning six decades, suggests that American presidents typically see their approval ratings soar in the immediate aftermath of a crisis, and continue to rise for two months. They then gradually fall back to previous levels over the course of a year. For Mr Trump this “rally round the flag” effect has been far less pronounced, lasted a mere 26 days and is on track to fade in just two months.

American politics is so polarised it is fair to assume that half of the country is hoping Mr Trump’s public image will improve at this historic juncture, just as the other half hopes it will deteriorate. The data, however, suggest another, even more striking, outcome: that support for Mr Trump will remain completely unchanged.