Global threats mount, and on top of the heap a jester gesticulates, roars and guffaws. The United States – no, the world – is in thrall to the Donald Trump reality show, on many days commanding more TV time and newsprint than the rest of the candidates for the presidency combined. The would-be leader of the free world has not spent a day, not an hour, on public service The Celebrity Apprentice statesman has not served a political apprenticeship of any kind.

They love him for it. Cleansed by wealth and fame, he has not been besmirched by active politics.

It’s still unlikely, but no longer inconceivable, that he will be president. Nate Silver of Fivethirtyeight, the man who generally calls it right on how elections go, is still skeptical that he will win the nomination, but much less so. He writes that “things are lining up better for Trump than I would have imagined… it’s not his continued presence in the race that surprises me so much as the lack of a concerted effort to stop him.” The trouble is, the people who would stop him are the Republican establishment. Politicianssss… hiss!

What, then – taking this a stage further than Silver is yet prepared to do – would President Trump find when he reaches the Oval Office, and the files thud on to the desk (he might, of course, sweep them to the floor and shout to his aides – “Expel the Mexicans! Build that wall! Keep out the Muslims! Tell the Chinese to get lost! Get that nice guy Putin over here!).

But suppose he decided to govern.

Trump’s predecessor, whom he abused daily, tried hard, in his first term, to “reset” relationships – with President Vladimir Putin of Russia (for which the phrase was coined); with the leaders of the Middle East, deeply resentful over George W Bush’s war on terror; and when he arrived on the scene as president in 2012, Xi Jinping of China.

He was very nice to the Europeans too — I attended a speech he gave in London’s echoing, mediaeval Westminster Hall in May 2011, when he declared that “there are few nations that stand firmer, speak louder, and fight harder to defend democratic values around the world than the United States and the United Kingdom.” And he clearly highly esteems Chancellor Angela Merkel, even if his spooks likely hacked her cellphone. (More leaks this week from Edward Snowden’s trove of NSA documents claim to show they tapped Silvio Berlusconi’s phone when he was prime minister too – especially when he was making calls to Putin)

Yet for his pains, he has given Russian and Chinese nationalism – powerful and scary engines, both – a shared doll in which to stick needles. Putin, the world’s most determined anti-westerner, gave a speech of incendiary force in March 2014 – saying that the Western states “prefer not to be guided by international law in their practical policies but by the rule of the gun… they act as they please…decid(ing) the destinies of the world, that only they can ever be right.” Pressing a spring (Russia) to its limits was dangerous, he warned, for “it will spring back hard.” Since then, it has only got worse.

It’s a little better with China, but not much. Xi’s trip to talk to Obama in Washington in September wasn’t a shouting match but little was agreed – little, that is, when set against the scale of the issues the two most powerful states in the world have before them. Earlier this month, Xi ordered the news media – including foreign media working in China – to obey the Party dictates: he’s closing up ranks as growth slows, and he fears disaffection in the country and in a Party he is seeking to cleanse. The West is a handy punch ball to which to divert aggression.

Many of the leaders in the Middle East whom Obama sought to reassure are gone, swept away by the “Arab Spring,” which he lauded in the London speech. Then the Spring itself was swept away, and new autocrats appeared, or chaos reigns. The Europeans love him (except when a row over phone hacking erupts) – but the European Union nearly lost its currency, it is losing its no-internal-borders policy and it is unable to be a full partner to the United States.

What has been lost in this? Perhaps the world itself. The challenges facing world leaders now are greater than anything in the post-Cold War period. In a book out next month, the Russian expert Robert Legvold lists some of them: they include trying to master the rapidly approaching second nuclear age, in which states with aggressive intent toward their neighbors (Pakistan and India; in the future, perhaps, Iran and Israel; North Korea and much of the rest of the world) are seeking to build nuclear arsenals.

The list includes, too, grasping the nettle of climate change, realizing that it is already too late to stop the rise of the oceans and the damage it will inflict on mainly poor, low-lying countries – and devising strategies to relieve mass distress as well as to prevent the warming becoming still worse.

It contains developing fruitful negotiations on the future of the Arctic, which at present, it seems, Russia will unilaterally militarize.

Political leaders have never operated as globally as they do now; the globe had never been so threatened by massive destruction as it is now; it has never needed joint action, agreements with substance, an end to feuds, as it does now. But we find ourselves, not in a new and hopeful era, but in a return to a cold war that could make the world cold and dead.

While a man with a growing chance of being the leader of the free world grins and waves and bellows – “We’re winning, winning, winning the country, and soon the country is going to start winning, winning, winning.”