IT IS almost exactly a year since I was sitting in the green room in a New York TV studio, chatting to an American political pundit, while we waited to go on — me to talk about Pope Francis, and he to talk about Donald Trump’s campaign to be president. “That couldn’t seriously ever happen,” I remarked lightly. “Just wait and see,” was his reply.

Well, I waited, and this week Mr Trump, now the official Republican nominee for the presidency, went head-to-head in debate with his Democrat rival Hillary Clinton. It has been a sobering 12 months, in which the Brexit vote has taught the British political elite the error of underestimating the capacity of an angry and alienated electorate to do the unexpected. It is a lesson that has registered in the United States, too, where Brexit is cited surprisingly often by political commentators seeking to explain to themselves the popular appeal of Mr Trump.

It is often said that gladiatorial debates are rarely game-changers: they just confirm viewers in the prejudices they had about the politicians before the programme began. And yet anyone who set out with the notion that Mr Trump was a joke candidate, and who watched the full entertaining 90 minutes this week, would have been left in no doubt that Mrs Clinton has a formidable rival.

The Republican nominee went toe-to-toe with his Democrat opposite number, and looked every inch her equal as a political force. Of course, he lacks real substance, but, as the Brexit vote taught us, a populist ability to harness voter discontent can be an effective substitute for that.

To my eyes, Mr Trump was scary. He bullied and blustered and tried to beat his opponent down with loud, unrelenting torrents of words. He played on electoral fear, greed, and delusions of American exceptionalism. Mexicans, Muslims, lawless blacks, and freeloading foreigners were all in his gunsights. But, as Abraham Lincoln is believed to have said, people who like this sort of thing will find this the sort of thing that they like.

Mrs Clinton landed some heavy hits, however. She pointed out that Mr Trump had made money from the housing crisis that predicated the 2008 global meltdown. To his response “That’s called business,” she countered that such “business” had lost nine million people their jobs and five million people their homes. And when she suggested that he paid nothing in federal taxes, his retort — “That makes me smart” — made him sound dumb.

And yet it is inescapable that, to his supporters, his presentation of himself — as a savvy businessman who understands money better than the politicians — is attractive. “I know you live in your own reality, Donald,” Mrs Clinton parried, after another brazen Trump untruth. But it is a reality shared by many who are disillusioned with the political Establishment that she represents. As with Brexit, kicking the cat seems an apt response to many voters who feel despised and excluded.

I am off to the United States again next week (to give another lecture on the Pope). It will be interesting to see how things look on the ground there now.

Paul Vallely’s biography Pope Francis: The struggle for the soul of Catholicism, is published by Bloomsbury. www.paulvallely.com