When Donald Trump announced his intention to run for president on June 16, few people took him seriously. His grand entrance, down an escalator at Trump Tower, to the sound of Neil Young’s Rockin’ In The Free World, was brash and bombastic and gloriously absurd. He had talked up his candidacy in every election cycle since the turn of the millennium. Won’t Get Fooled Again by The Who would have been more appropriate.

His speech was a chilling piece of far right political theatre. He promised to build a “great wall” on the USA’s southern border “and have Mexico pay for that wall”. He declared that the real unemployment rate is 20% and that he would be “the greatest jobs president that God ever created”. He claimed health insurance under Obamacare is so thin that “you have it get hit by a tractor, literally, a tractor, to use it,” boasted that his net worth is $8 billion and mocked his Republican rivals for sweating “like dogs” under pressure.

The following day, the front page of the New York Post carried a picture of the White House with Trump spelled out above the columns in gold. Like the boy in Aesop’s fable, 'The Donald' was hard to believe, but if he got eaten by a wolf, what a story it would be. Four years ago, the American media built up Republican contenders Michele Bachmann, Rick Perry, Herman Cain, Newt Gingrich and Rick Santorum in turn, only to knock them down. Most analysts predicted that Trump’s campaign would collapse at the first hint of scrutiny.

In July, when Trump said that Senator John McCain is “not a war hero,” the press rushed to write him off. In August, when he issued a misogynistic tweet that Fox News presenter Megyn Kelly had “blood coming out of her eyes, blood coming out of her wherever” at the first Republican debate, wise heads opined that a war with the news network would be his undoing. In September, when he played along with a man who suggested that President Barack Obama was Muslim and “not even American,” the same commentators wrote that this time he was finished.

To judge by coverage of his campaign, it is forever the beginning of the end for Trump. But what if it isn’t? In every poll since he entered the race, he has been the clear front-runner. On Thursday CNN’s latest survey showed him with a lead of ten points over his nearest rivals, Ben Carson and Carly Fiorina. Jeb Bush, for so long the ‘inevitable’ candidate with the most endorsements and the biggest war chest, was a further five points back.

No doubt, name recognition accounts for some of this. The Apprentice is in its fourteenth season on prime time television, and Trump has been a public figure since the 1970s. The Fox debate attracted 24 million viewers: other than sporting events, the largest cable audience ever. 'The Donald' is a ratings bonanza and therefore gets more free publicity than the other candidates combined.

He is also, in this obsessively media-managed, on-message era, seemingly 'authentic' - though you have to be of a certain temperament and political persuasion to find his brand of authenticity appealing, rather than bullying, bigoted and offensive. When I interviewed him some time ago, in his office at Trump Tower, lined floor to ceiling with pictures of his own face, he talked at length about the golf links he was planning for the Aberdeenshire coast. From start to finish, his chat was text book big shot.

At one point the phone rang. Would I mind if he took it? His daughter in California was worried about forest fires. “Well how far away is the smoke? I’ll buy you another house if it burns down, honey, OK?” On the way down to the set of the Apprentice, he introduced another daughter, Ivanka: “This is Andrew, he’s going to write a bad story on me… But you know, I’ll get over it, I’ll keep going. Who else has had more bad stories written about them than me?”

As his presidential run has gathered momentum, the “bad stories” have piled up, notably in right-leaning publications that previously treated him as one of their own. The National Review and the Wall Street Journal editorial page have been scathing in their attacks. Prominent conservative columnists George Will and Charles Krauthammer have put the boot in. They know that in a general election, Trump’s sexism and anti-immigrant rhetoric are a liability for the GOP brand. But in a crowded primary, they might just win him the nomination. And that frightens them.

On September 21, Wisconsin Governor Scott Walker withdrew from the contest and called on others to do the same “so that the voters can focus on a limited number of candidates who can offer a positive, conservative alternative to the current front-runner”. The Republican establishment is panicking - they want to, and need to, finish Trump off.

Trump’s promise to deport more than ten million undocumented immigrants and repeal the Fourteenth Amendment to the Constitution that guarantees US citizenship to anyone born in the country has made him a hero on the hard right. Pundit Ann Coulter wrote that he is “leading on the seminal issue of our time while the rest of the field practices looking optimistic in front of the mirror.”

His language about migrants from Latin America - “they’re bringing drugs, they’re bringing crime, they’re rapists, and some, I assume, are good people” - has attracted some unsavoury allies, including neo-Nazi website the Daily Stormer, which has endorsed him for president.

On Wednesday, on the campaign trail in New Hampshire, Trump suggested that the Syrian refugee crisis could be “one of the great tactical ploys of all time,” and expressed disgust that the USA would consider taking in asylum seekers. “They could be ISIS,” he warned. “They are all men and they are all strong.”

Trump’s popularity among evangelical Christians is harder to fathom. Despite being on his third marriage and once describing himself as “very pro-choice” when it comes to abortion law, he is the leading candidate for voters on the religious right. Asked to name his favourite book, he chooses the Bible but his description of taking communion - “I drink my little wine… and have my little cracker” - is glib in the extreme. Some would say phoney.

Polls show that Trump’s supporters tend to be older, whiter and less educated than Republican voters as a whole. Men are more likely to back him than women, but not by much. The campaign slogan that he wears on his hat - “Make America Great Again” - may be borrowed from Ronald Reagan, but it is simple and effectively blunt rhetoric.

His personal wealth, estimated by Forbes magazine at $4.1 billion (roughly half what he claims) means he is not beholden to wealthy donors, a huge political asset in these times of unlimited campaign donations and naked corporate influence. When his rivals attended a retreat hosted by Republican king-makers Charles and David Koch, he tweeted: “I wish good luck to all of the Republican candidates that travelled to California to beg for money etc. from the Koch brothers. Puppets?”

On the stump, he speaks without a tele-prompter - and seemingly without a mental filter - lending his remarks an unpredictability and bluntness that many voters perceive as authenticity. He is crass, rude and trades in catty one-liners: “We give state dinners to the heads of China. I say 'Why are you doing state dinners for them? They're ripping us left and right. Just take them to McDonald’s and go back to the negotiating table’.”

He is also astonishingly, unrepentantly ignorant, and brushes off questions about policy specifics by saying that he is a great delegator and will surround himself with “the smartest, toughest, best people” in office. This too is part of his appeal: a platform so vague that voters can fill in the blanks. Obamacare is a disaster, Trump says, but don’t worry. “I am going to take care of everybody…Everybody’s going to be taken care of much better than they’re taken care of now.”

This mixture of meaningless rhetoric, vacant policy, and hate-filled speech is both his strength and his weakness - and it is also what makes him frightening to many ordinary Americans, both Republican and Democrat. There is a real fear about where American could go if it was led by a man like Trump with such demagogic leanings.

Other than his immigration proposal, the only part of his manifesto that he has outlined in any detail is his taxation plans. Trump poses as a populist, by saying he will make corporations and “hedge fund guys” pay their share by closing loopholes, but his published plan reveals him to be an orthodox, if rather extreme, supply-side Republican.

If elected, he will eliminate the estate tax, cut the top rate of federal income tax from 39.6% to 25%, cut the corporate tax rate to 15% and raise the threshold for the lowest rate of income tax to married couples to $50,000 per year, meaning 95 million households would pay no federal income tax at all. Trump predicts that the economy will grow so much as a result that the cuts will be revenue neutral, a claim that even conservative economists find hard to entertain.

It's a mark of just how much he has alienated many traditional Republicans, however, that Conservative anti-tax lobby group Club For Growth, is running adverts against him in Iowa, the first state to vote, describing Trump as “the worst sort of politician” and playing a clip of him telling CNN: “In many cases, I probably identify more as a Democrat.”’

The primary calendar could suit Trump. If he can make it through socially conservative Iowa and maverick New Hampshire (he leads in both) a series of big, winner-takes-all states in March could provide most of the delegates he needs to secure the nomination.

His two closest rivals at present are Carson, a former neurosurgeon who believes evolution is a lie, calls Obama a “psychopath” and equates today’s USA with Nazi Germany; and Fiorina, whose tenure as CEO of Hewlett-Packard was marked by the loss of 30,000 jobs.

Trump’s ad hominem jab that Bush is a “low energy person” has hit the mark. There is still time for a moderate establishment candidate to rise - Ohio Governor John Kasich perhaps - but the fringe candidates most likely to drop out, such as Senators Rand Paul and Ted Cruz, are hardliners whose support would presumably gravitate to Trump.

On September 23, Trump announced, for a second time, that he would not be appearing on Fox News “for the foreseeable future,” because the network had been treating him “very unfairly”. For readers who may be unaware Fox is a nakedly right-wing TV channel that acts as the mouthpiece of the Republican Party and demonises Democrats. That perhaps gives you a measure of just how extreme Trump is in the USA. Fox fired back that it had, in fact, withdrawn his invitation, adding that “candidates telling journalists what to ask is not how the media works in this country.”

The irony is that Trump is the definitive Fox Republican. His candidacy was made possible by a conservative media that fosters cultural resentment and feeds on the spectacle of combat. Its constituency is fed up, suspicious of all politicians and ready to believe in a charismatic outsider who gets things done. “If I am president, you're going to be so proud of this country,” Trump tells them. “You will be the happiest people.”

In a country built on the American Dream, it is hard not to think of the literary critic Cyril Connolly's description of F Scott Fitzgerald's masterpiece The Great Gatsby when listening to Trump's empty and meaningless promises: 'His style sings of hope; his message is despair.'