SO how did it come to this? How did a nation founded on self-evident truths move into the post-truth era?

How has it become part of political strategy to tell lies and when they are challenged respond by just shouting them?

Every presidential race has a motif or even a slogan but the 2016 version has been marked by such outlandish rhetoric that it makes it a phenomenon. Recent reading of two books has franked my belief that politics is now firmly in the era when the Big Lie is not a gaffe or even a piece of verbal mischief but a strategy. It is depressing, demoralising. But how did a country come from presidents of principle to opportunistic challengers?

The chasm is clear when reading David McCullough’s extraordinary1982 portrayal of John Adams, the second president, then turning to the devastating indictment of Donald Trump by Washington Post journalists Michael Kranish and Marc Fisher.

A founding father, Adams, served from 1797 to 1801. He could be vain, he was certainly stubborn and occasionally irascible but he was guided by principle. As a lawyer, he represented the British soldiers who shot rioters in the Boston Massacre. He was thus defending people who had shot those who shared his views.

This cost him money and brought him criticism. He believed, however, that everyone deserved the best defence possible. “Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence,” he said. He won the acquittal of six soldiers.

Adams then served as a diplomat, ensuring the young US Government could be nurtured in times when independence was fragile. He also signed the Declaration of Independence which celebrated the self-evident truths of equality and life, liberty and the pursuit of happiness. He was, then, a man of substance.

The Trump story is gaudy, even lurid. There is conspicuous consumption, there are allegations of sexual assault, there are questions over many of his most lucrative deals.

He comes from a privileged background of a wealthy father. He has never served, he has always been served.

Fact fan: Massachusetts farmer-lawyer John Adams

But it is his rhetoric that separates him from the mass of presidential candidates. Hillary Clinton, after all, has been anointed by the balm of privilege. She also has been involved in scandal, though never brought down by it. She is a flawed candidate. She, too, has been caught in untruths.

However, it is the scale of the Trump deception that makes him the outlier of liars. It is also the reality that these lies have not damaged him but rather have taken him into contention for the most powerful role in democracy. The assumption, given recent polls, is that the businessman from Queens, New York, will fail in his presidential bid. But how has he come to the run-off with a past that is shady at best and a present that is filled with astonishing revelations and desperate rebuttals?

The truth, of course, is that Trump is not the first man to run for president on a background of questionable business deals and predatory, perhaps even criminal, sexual behaviour. His unique selling point is his genius – and it is all of that – for telling lies. His past is littered with them, with investigative journalists finding facts that Trump simply denies.

It could be described as the behaviour of the toddler covered in chocolate who swears he never touched the selection box. But it serves a bigger purpose in politics. If this is the era of post-truth, then Trump is its standard bearer.

He writes in the Art Of The Deal:

“I play to people’s fantasies.” He thus not only tells people what they want to hear but what they crave to hear. This works best when it is addressed to those who considered themselves disenfranchised and lost, most particularly white working class men who are either unemployed or in menial jobs.

It was Hillary Clinton’s husband who articulated what was believed to be the eternal big truth of the decisive factor in American elections. “It’s the economy, stupid,” was his mantra.

But not now it ain’t, at least in obvious terms. The American economy is in decent shape, certainly healthy enough to promote the chances of the incumbent party. Median household incomes rose more than five per cent in 2015. Businesses have added more than 15m jobs since 2010, house prices have bounced back, the stock market has recorded near record highs.

However, many Americans do not feel this, do not believe this. They prefer, instead, to invest in the Trump rhetoric. This is real to them. The story of a failing nation that was once great, the narrative of immigrants coming to work on the cheap, the theory of the USA being slowly diminished by poor trade deals and threatened by coming economies all speak to their fears.

It also reflects their sense of being lost in their own land. There is an undeniable problem of poverty in America. It embraces both the paucity of material wealth and that of hope.

These issues must be addressed but Trump has only the absurd to offer rather than concrete policy. Yet many who need substance in politics and in their lives are attracted to the chimera of The Donald.

THIS is a powerful mojo. It is why there are two strong lessons from the Trump campaign. The first is that a candidate employing the Big Lie, without the awful personal excesses of Trump, could have won this election. The second is that refutations are seen not as facts but liberal lies. The perspective is dangerously skewed, perhaps irrevocably so.

Many people now do not access their news or opinion from mainstream sources but from sites that reinforce their prejudices. The Big Lie grows bigger.

One hears its march in the roars that greet every Trump statement in debate or at podium. But it has, of course, already crossed the Atlantic.

The reality of modern politics is that the Big Lie can win big. Trump may fall short but the Brexit campaigners with their dreadful posters and their lies written on the side of buses did not.

The lesson is that politics once aspired, certainly in the days of John Adams, to meet people’s hopes. Now politicians seek to prey on fear. It was thus in the Scottish referendum campaign and it was so in the successful Brexit strategy.

In the sheer extravagance and regularity of his lies, Trump has become both vilified and cheered. He has also walked to the very edge of extraordinary power. He may yet confound the polls and become the most powerful politician in the world.

This may be unlikely but there is a deeply unsettling development personified by Trump. In the age of post-truth, the Big Lie is king. This has its lessons for the USA. It may also have a resonance when indyref2 comes around.

Trump Revealed: An American Journey of Ambition, Ego, Money and Power by Michael Kranish and Marc Fisher, Simon & Schuster, 2016

John Adams by David McCullough, Simon & Schuster, 2002