Nations, as the scholar Benedict Anderson put it, are “imagined communities”. America’s crisis is that its imagination is breaking into two. On the one hand there are Donald Trump’s nationalists. On the other are the globalists. These are people who want “the globe to do well, frankly not caring about our country so much”, in Mr Trump’s words. His definition is both offensive and ingenious. It also plays with fire. The improvised explosive devices mailed this week to George Soros, Barack Obama and Hillary Clinton might as well have been addressed “globalist”.

The looming midterm elections are a custody battle over which side owns the American creed. Mr Trump’s critics embrace the term patriotism but declare nationalism taboo. Yet there is nothing inherently racist — or violent — about being a nationalist. Ask most people in India, or Ireland, and they will unashamedly own the label “nationalist”. Their republics were forged after the word was coined. The US republic was born earlier. In the late 18th century nationalists called themselves patriots. In fact, most American liberals are nationalists. They believe their country’s creed is better than others. It is thus worth fighting for. Splitting semantic hairs is no answer to Mr Trump’s challenge.

Nor is it much use pointing out his factual errors. Mr Trump says that the 7,000-strong caravan of central Americans heading to the US border is riddled with Middle Eastern terrorists and members of drug gangs. Moreover, the caravan is being led by Democrats. People such as Mr Soros are funding the advancing mob. They are trying to stage a globalist takeover, which makes them un-American. Each of Mr Trump’s claims is disprovable. But that is not the point. They play into his base’s imagination. Mr Trump’s nationalism is not gentle. But even the mildest sort requires some suspension of disbelief. As Anderson put it: “Members of even the smallest nation will never know most of their fellow members, meet them, or even hear of them, yet in the mind of each lives the image of their communion”.