When Donald Trump took to the stage at the UN General Assembly last week, he had a seemingly endless list of the USA’s triumphs to show off to the world leaders gathered in New York.

“America is back, and our country is stronger today than ever before,” he began. “Our economy is the envy of the world. Our military is the most powerful on earth. Our technology is second to none, and we are leading in virtually everything. Our energy is fuelling the planet. America is rising.”

There is, of course, nothing wrong with taking some pride in your achievements. But Trump wasn’t done – he continued bragging in front of the assembled dignitaries for quite some time, before eventually going on to threaten Iran with annihilation, almost absent-mindedly.

Except a roomful of politicians, even if some are dictators rather than democratically elected, would be able to see the problem with Trump’s words in no time. If things are going so well, then why do Trump’s approval ratings keep hitting new lows almost every other day? Why are Republicans worried about a wipeout in the midterms – with states Trump won by double digits just two years ago now hotly contested? And why does Trump seem so relentlessly angry?

However brave a face Trump was putting on for world leaders, he is clearly aware on some level that things aren’t going to plan. On Truth Social, he occasionally launches furious tirades about biased polls, promising that the real ones show he’s still beloved. His new war against the “fake news” media is another sign he’s unhappy about the coverage.

But neither of these is the root of all of his discomfort. Instead, it’s surely the economy. The stock market is doing fine, boosted by huge investment in AI – even if some are worried that’s a bubble which could pop at any time – but the rest of the economy is struggling. Food is getting more expensive, job growth is slow, and the affordability crisis that clearly bored Trump so much is only getting worse.

When it comes to the economy, though, it’s the price of oil and gas that matters more to everything else – both to Trump and to the economy at large. When oil and gas are expensive, everything else gets expensive: it costs more to move products around, energy costs more, and so manufacturing is more expensive; tractors use diesel as they work farms, pushing up food prices.

By starting a war with Iran, Trump pushed up oil and gas prices, especially once the Iranian regime managed to largely shut off the Strait of Hormuz. At first, experts thought this would cause an immediate and persistent spike in oil and gas prices – but Trump managed to prove them wrong, at least for a time.

Trump’s conflict with Iran started in spring, when oil and gas use for heating drops. Trump managed to convince everyone the conflict would be short, and so countries turned to their national reserves.

Beyond that, he discovered a fantastic trick: time and again, Trump would promise that a peace deal or a ceasefire to reopen the Strait of Hormuz was going to be signed any day now. Time and again, global markets believed him.

For most of the year, oil prices have been higher, but not dramatically so. Traders genuinely seemed to believe Trump would have the Iran war wrapped up long before the midterms – and, crucially, long before the northern hemisphere entered the winter months.

As a famous TV show once said, winter is coming. Countries have spent most of the year burning their oil and gas reserves, and they are now running low. The Strait of Hormuz isn’t open, and for a time the east-west pipeline across Saudi Arabia wasn’t working, either. Suddenly, the prospect of oil and gas shortages in the dead of winter looks all too real.

Donald Trump is trying to sound positive. But even he isn’t managing to promise peace deals quite as often as he used to. Where once he promised a ceasefire was coming any day now, he’s now saying it will come just after the midterms, honest.

That’s leading even the most credulous of observers to wonder why Trump would delay a popular peace deal until after ballots were cast – and to conclude that maybe he doesn’t have a plan to end his oil crisis, after all.

Most Americans are already deeply unhappy with Donald Trump and his administration’s performance, including millions of the people who voted for him just two years ago. But we may have seen nothing yet: if Trump doesn’t magic up a real deal, and soon, oil and gas will soar, inflation will rise with it, and his popularity will explore still new depths.

Trump’s “trust me” trick has got him through the summer. It will take much more to get Trump – and America – through the winter.