All right, so Donald Trump looks slightly less likely to become the next President of the United States than he did a week ago. He was soundly beaten by Ted Cruz in the Republican primary in Wisconsin, a swing state that may be a more accurate gauge of overall electability than most. Nor has he given any even a hint of reining in his unguarded self, although his statements on abortion could already have cost him a large part of the female vote.

But the fact that this untamed politician says things that are widely unacceptable, or just plain daft, does not automatically make everything he says wrong. As with George Galloway here at home, it well suits those who disagree with him to damn all his views by association. But there are times when an innocent or an iconoclast speaks a truth that others are unprepared to face.

Trump’s description of Nato – the hallowed North Atlantic alliance – as “obsolete” is a case in point. His terseness may have shocked, but he is right.

So are his reasons. As currently constituted, he says, Nato is ill-suited to combating international terrorism, which is for him the world’s “single biggest threat”. He especially objects to the US footing so much of the bill, saying that other allies should “pay up or get out”, and refuses to see the US as the “world’s policeman”. As he told a town hall meeting in Wisconsin: “Maybe Nato will dissolve and that’s OK, not the worst thing in the world.”

To judge by the response to his words, though, on both sides of the Atlantic, it would appear to be the worst thing, or close to it. In casting doubt on the future of Nato, Trump has challenged an establishment consensus that goes far beyond Washington DC. Both Trump’s Republican rivals have denounced his view. Hillary Clinton, the probable Democrat nominee, accused him of “putting at risk the coalition of nations we need to defeat Islamic State”.

Practically every general and admiral between the US and the Baltic States reached for their verbal swords. Every transatlantic think-tank, every Atlanticist professor, and even President Obama joined the fray. Trump’s words, said Obama, had shown that “he doesn’t know much about foreign policy or nuclear policy... or the world generally”.

It is worth noting a couple of ironies here. Obama is on the record – in his last State of the Union address and in his recent Atlantic magazine interview – as rejecting, more explicitly than any of his immediate predecessors, a “world policeman” role for the US. Both he, and his former defence secretary, have also criticised the lacklustre contribution to the alliance of some Europeans. To question Nato’s very existence, however, is another matter. For a sitting president, countenancing the twilight of the North Atlantic alliance is a step far too far.

There are times, though - and this is one of them - when a measure of distance and “not knowing” may foster much-needed clarity. Seen from the perspective of 2016, the North Atlantic Treaty Organisation is not only “obsolete”, but has been so in spirit since 1989, when the Berlin Wall fell, and in fact since the end of 1991, when the Soviet Union collapsed.

The end of the Cold War should have celebrated, and made final, by the dissolution of both the alliances of the era. In the event, only the Warsaw Pact was wound up. Nato survived, and has spent the best part of 30 years casting around for something else to do.

There are reasons why Nato was not disbanded. Some are understandable: there was so much going on, so many uncertainties to deal with, that there was no time to take on additional distractions. Nato also offered an element of solid security in a suddenly fluid world. Other reasons are, in their way, admirable. Those countries now freed from the extinct Soviet bloc still feared Russia and sought the defensive shelter they believed Nato could provide. The mistake was less to admit them, almost a decade later, than that the alliance was still there.

Donald Trump's most controversial quotes Show all 14 1 /14 Donald Trump's most controversial quotes Donald Trump's most controversial quotes On Isis: "Some of the candidates, they went in and didn’t know the air conditioner didn’t work and sweated like dogs, and they didn’t know the room was too big because they didn’t have anybody there. How are they going to beat ISIS?" Getty Donald Trump's most controversial quotes On immigration: "I will build a great wall — and nobody builds walls better than me, believe me —and I’ll build them very inexpensively. I will build a great, great wall on our southern border, and I will make Mexico pay for that wall. Mark my words." Reuters Donald Trump's most controversial quotes On Free Trade: "Free trade is terrible. Free trade can be wonderful if you have smart people. But we have stupid people." PAUL J. RICHARDS | AFP | Getty Images Donald Trump's most controversial quotes On Mexicans: "When Mexico sends its people, they’re not sending their best. They’re sending people that have lots of problems. They’re bringing drugs. They’re bringing crime. They’re rapists." Getty Donald Trump's most controversial quotes On China: "I just sold an apartment for $15 million to somebody from China. Am I supposed to dislike them?... I love China. The biggest bank in the world is from China. You know where their United States headquarters is located? In this building, in Trump Tower." Getty Images Donald Trump's most controversial quotes On work: "If you're interested in 'balancing' work and pleasure, stop trying to balance them. Instead make your work more pleasurable." AP Donald Trump's most controversial quotes On success: "What separates the winners from the losers is how a person reacts to each new twist of fate." Donald Trump's most controversial quotes On life: "Everything in life is luck." AFP Donald Trump's most controversial quotes On ambition: "You have to think anyway, so why not think big?" Getty Images Donald Trump's most controversial quotes On his opponents: "Bush is totally in favour of Common Core. I don't see how he can possibly get the nomination. He's weak on immigration. He's in favour of Common Core. How the hell can you vote for this guy? You just can't do it." Reuters Donald Trump's most controversial quotes On Obamacare: "You have to be hit by a tractor, literally, a tractor, to use it, because the deductibles are so high. It's virtually useless. And remember the $5 billion web site?... I have so many web sites, I have them all over the place. I hire people, they do a web site. It costs me $3." Getty Images Donald Trump's most controversial quotes On Barack Obama: "Obama is going to be out playing golf. He might be on one of my courses. I would invite him. I have the best courses in the world. I have one right next to the White House." PA Donald Trump's most controversial quotes On himself: "Love him or hate him, Trump is a man who is certain about what he wants and sets out to get it, no holds barred. Women find his power almost as much of a turn-on as his money." Getty Images Donald Trump's most controversial quotes On America: "The American Dream is dead. But if I get elected president I will bring it back bigger and better and stronger than ever before and we will make America great again." GETTY

The collapse of the Soviet Union was a lost opportunity for a new security settlement across the whole of Europe. But a second opportunity was lost, too. During the late 1990s there were tensions between the US and the European Union, which had begun to harbour defence ambitions of its own. While Washington was all in favour of its European allies taking a greater interest in their own security, it did not want them to run their own show. Had the Europeans asserted themselves more, had the British been better Europeans, had Nato expansion not obscured the dilemma, the EU might now have its own defence union, albeit not without a – possibly unpleasant – split with Washington.

It is tempting to look back at what might have been - and specifically what different security arrangements for Europe might have prevented. The obvious example here is the Ukraine crisis and the new stand-off with Russia which gives Nato a revived (and thoroughly regrettable) purpose. In the end, though, perhaps the least contentious way for Nato to bow out would not be in a new 1991-style cataclysm, nor for the Europeans to declare defence independence, but for the US to conclude that the alliance is no longer in its national interest.