Soon after I arrived in Washington DC in the autumn of 1993, I found myself in a dinner-table argument with one of the many deeply liberal Washingtonians who populated the diplomatic and media circuits of that strange, lovely, melancholy city.It increasingly strikes me, when I now visit it, as a beautiful cemetery of vast, imposing sepulchres in which various deceased ideas lie at rest among lakes and woods.

He obviously despised my social conservatism, was shocked that I dared articulate it in such a place, and addressed me more or less as you would speak to something you had found stuck to the underside of a café table.

I said that he should show me more consideration. I was, I pointed out, civilised, polite, a believer in freedom of speech and the rule of law, tolerant of opponents and inclined to listen to them. I was literate, informed, reasonably cultured. I felt very strongly that he and his faction were wrong to push their programme so hard – especially sexual revolution and mass immigration. I thought it was wrong anyway. I also thought that it would in the end infuriate so many people that it would endanger free society.

They should listen to people like me while there was still time, or they might find they had other, less loveable opponents to contend with.

Out of the blue, I found myself saying ‘This life and state of affairs, which we enjoy here, and which you seem to think will go on for ever the way you want it to, could turn out to be the Weimar Republic.’

He turned away contemptuously and did not speak to me again that evening. I cannot now even recall precisely who he was or exactly where it was, I remember one of those large DC houses, or perhaps it was over the line in Maryland, or Northern Virginia, surrounded by wooded slopes in which the cicadas shirred and chirruped in the warm darkness.

The thing about Weimar, as far as one can see, is not that it ended precisely with the Nazis. That will never happen again. It was that nobody who lived in it really had any clue that it would finish so abruptly, or what was coming next, until the very end. Nor did they grasp how much their own liberalism was resented and how swiftly and absolutely most of it would be undone in the reckoning that followed.

Despite the myth of ultra-liberated 1920s Berlin, Weimar was in many ways a much more staid and conservative society than the ones we inhabit in post-Cold War Britain and the USA.

The social experiments of our time are far bolder, the abandonment of old rules far more complete and comprehensive. There isn’t a corner of our society which has not felt it, and TV brings it swiftly into every home.

But what about the economics? The refloating of Germany after money died, much of it done by that fishy wizard Hjalmar Schacht, was a confidence trick based on land values (and later off-the-books loans) not all that much more wobbly than the confidence trick by which our own wildly indebted economy (and that of the USA) totters onwards on the tightrope, into the mist, unable to tell when or even if it will reach solid ground again.

We have actually had a great crash in 2008, but managed to paper it over. Nobody really knows when it will return, but many fear it will.

And now along comes Donald Trump. I am amazed to find some conservatives enthusing about this person, who until quite recently was a keen defender of abortion, a donor to Hillary Clinton’s senatorial campaigns and to the Clinton Foundation (Mrs Clinton attended Mr Trump’s Palm Beach wedding, in 2005, to his current wife, Melania, and ex-President Bill came to the reception).

Likewise, Mr Trump’s personal life, though of course his own business in the modern world, does not exactly conform to the Christian ideal which most American conservatives espouse.

So, whoever may delight in Mr Trump’s advance, I shouldn’t have thought any principled conservative could do so.

I am also troubled by his extravagant promises – to build a wall along the Mexican border, to bar Muslims from entering the USA (how?) ; and by the crudity of his slogans. I don’t get the impression Mr Trump is an especially cultured or historically-informed person, but I am pretty sure he is a cunning and astute one (these two sets of qualities rarely coincide in any human being). He knows perfectly well that such things are, shall we say, going to be very hard to fulfil in practice. Likewise his enthusiasms for protecting America’s many dying industries. I’m a protectionist myself, unbeguiled by the siren song of free trade, but even I can see that these pledges may be a bit hard to fulfil in practice in two terms, let alone one.

In any normal time, his success would have been headed off, as was Ross Perot’s similar (but less outrageous) campaign back in 1992. In fact, Perot was far more realistic. The North American Free Trade Agreement was still unsigned when Perot campaigned against it, and US domestic industry was a lot healthier and more protectable then that it is now.

Meanwhile, though the Mexican border was terribly porous (as I saw for myself at the El Paso- Juarez frontier), the full effect of mass migration had yet to be felt, and the USA’s conservatives were still divided on whether to support or oppose it.

Both those policies, plus the sexual revolution and the de facto decriminalisation of marijuana, were continued and amplified during the next 20 years. The idiotic, bellicose, repressive response to September 11th discredited and divided what was left of conservative America, leaving nothing to define them but war abroad and the free market at home.

Even the abortion and death penalty issues, which allow American Republican politicians to pose as social conservatives without actually having to *do* anything, have worn pretty thin as vote-getters.

And so now here is Mr Trump, bellowing the cracker-barrel wisdom of ten thousand bar-bores over a national megaphone.

And the vast ignored heart of America, pushed to the margins and infuriated by decades of bilingualism, 'medical marijuana', same-sex marriage, political correctness and shrinking wages, falls for it.

While the Democrats, who have likewise run out of useful things to say and are in many cases reduced to nostalgic votes for that 1930s figure, Bernie Sanders, have no reply except the Clinton name, which is not that good a name in the end.

Is this how the great experiment in universal suffrage democracy ends?

For the last few weeks, thanks to a minor back injury which (by keeping me off my bicycle) has completely re-arranged all my days, I have been rather prone to a sort of melancholy foreboding, which is, as I well know, subjective and irrational. What I cannot now reliably do is to separate this from the equally melancholy foreboding, objective and rational, I now feel about the US general election, and our own increasingly banal and thought-free referendum, in which both sides are drawing very heavily on the Bank of Trust which (just as in the USA) is very nearly empty anyway. This is playing with fire. Can any of these people even begin to deliver what they promise, or prevent the things they rail against?

If not, what happens when the voters find this out?