The anger is etched on his face. The young white man wearing a red Donald Trump "Make America Great Again" shirt is screaming at some 30 protesters who have interrupted the Republican candidate's speech at a rally at Radford University, in Virginia.

“Right smack in the middle of my punchline,” says the billionaire, annoyed that he can’t finish explaining how, as president of the United States, he would slap a 35 per cent tax on goods made in Mexico coming into the country over his proposed wall.

"You're not angry people. You're not angry people," Trump tells a crowd of 3,000 supporters on Monday as he waits for security to remove the demonstration. "By the way, they're angry people," he adds, pointing to the protesters. "You're not angry people. You're people who have a great love for this country."

Trump is wrong. His supporters are furious: at the way politicians have betrayed them; at the way American jobs have been shipped overseas; at the way they haven’t received a real pay rise in years; and at the way their country is no longer the economic or political superpower it once was.

In the Super Tuesday ballots across a dozen states this week, in which the Republican and Democratic parties asked supporters to choose their presidential candidates – the biggest single day in the US presidential election so far – Trump surged ahead on the back of a huge turnout in his march to becoming the Republican nominee to fight the November 8th election to succeed the Democrat Barack Obama. The property developer added seven states, from Massachusetts, in the northeast, to Alabama, in the deep south, to three he won in February.

His angry anti-establishment campaign, fuelled by nationalistic, anti-immigrant rhetoric, has lit a fire under grassroots Republicans. His supporters are mostly the white, the poor and the less educated. They feel short-changed by an economic recovery that has really benefited only the wealthy and by a political system they believe represents only big-money interests.

Exit polls for nine states voting on Tuesday showed that many Republican voters were angry at the way government worked and felt betrayed by their politicians.

Support for Trump’s plan to ban Muslims in the aftermath of the Paris and San Bernardino attacks ranged from 64 per cent in Virginia to 78 per cent in Alabama. Those polls back up surveys in recent months showing that Americans are more afraid than at any time since 9/11.

Establishment alarms

Trump’s stranglehold on the race has alarmed the Republican establishment, which is concerned that his divisive candidacy may affect the party’s chances of regaining the White House and retaining a majority in the Senate, along with control of the Supreme Court. The latter hangs in the balance following the death of the conservative hero Justice Antonin Scalia.

Party elders in Washington must bear some of the blame. They didn’t just underestimate Trump: they also underestimated the anger among the voters who are propelling him towards the Republican nomination.

"Trump is sort of a stick-it-to-the-man candidate. Or, to use a line from the old movie Network, 'I'm mad as hell, and I'm not going to take it any more'," says Keith Poole, a professor of politics at the University of Georgia.

He likens Trump to the mountebanks, or snake-oil salesmen, of the Wild West, who sold elixirs from the back of horse-drawn wagons. “He is promising to make America great again,” Poole says, “but nobody really knows what that means. He is just basically an entertainer.”

Trump’s high-decibel rallies are long on rhetoric and short on detail. To raucous applause he says he would “bomb the s**t out of Isis”, but the US has been pretty much doing that since August 2014. He rubbishes Obama’s trans-Pacific trade deal, blaming China for currency manipulation, but China is not party to the deal. He promises to impose huge tariffs on Mexico and China, but that would violate binding trade agreements.

Trump’s supporters, cheering every promise he makes, see a strong man who can cure the country’s ills, who can transfer his reputation for hard dealmaking from the boardroom to the Oval Office. The complicated details don’t really matter.

“They don’t matter because many of them are angry, but alongside and underlying that anger is a sense of desperation,” says William Galston, an expert in governance at the Brookings Institution think tank. “It is the combination of anger and fear that does not put people in a particularly reflective frame of mind. This is the politics of the viscera, not the brain.”

No challengers

Trump has excelled in the absence of a single candidate to challenge him. The televised debates have shown his mastery of bullying rivals such as the “low-energy”

Jeb Bush

. “There is no strong figure or leadership there, and Trump has a kind of flatulent charisma and noise,” says Roger Daniels, an emeritus professor of history at the University of Cincinnati.

The noise has worked. Tuesday’s exit polls show voters chose Trump not for his policies but because of his outsider status and his willingness to “tell it like it is” – something he practises every day on Twitter.

In states Trump won this week, Republican voters cited the economy and jobs as their most important worries. They have much to worry about. Obama has boasted that more than 14 million jobs have been created since the 2009 recession, but they have been unevenly distributed. Middle-class jobs have disappeared, made redundant by technology. Unemployment in the 16-24 age bracket is 10.3 per cent, almost double the overall rate.

Nor have wages improved. The average family income was $53,657 (€49,400) in 2014, a decline from $57,843 (taking inflation into account) 15 years earlier. Since the 2009 crash 95 per cent of earnings growth has risen to the top 1 per cent of earners, according to the Institute of Policy Studies, in Washington. “The underlying cause of all this unrest in the United States is the dramatic increase in inequality,” says Poole.

US manufacturing has been in decline since the second World War, a trend Trump has promised to reverse, again without really saying how. The mogul regularly blasts companies for moving to Mexico. He has criticised the snackmaker Nabisco for relocating a bakery from Chicago, promising, “I’m never eating another Oreo again. I am telling you. Never.”

He bashes multinationals, regularly mentioning the drug company Pfizer for relocating to Ireland to avoid higher US taxes, and promises to reduce taxes on businesses to end this practice of “corporate inversions”.

The idyll that Trump paints for his disaffected base is a return to the halcyon days after the second World War, when the United States’ dominance was unquestioned. Trump’s “Make America Great Again” campaign slogan comes from Ronald Reagan’s 1980 presidential campaign.

Trump’s supporters view Obama as a weak foreign-policy president and believe that the tycoon will be different. His rise comes at a time when fewer Americans regard their country as the greatest on the planet. Pew Research found in 2014 that 28 per cent thought the US stood above all other countries, down from 38 per cent three years earlier.

Part of Trump’s simple plan to defeat Islamic State extremists is to find a general in the mode of George Patton or Douglas MacArthur, military leaders who evoke the country’s strongest days during the second World War. “That was a great time for America and the years immediately after. That was the middle of the American century,” says Daniels, who views Trump as a showman in the vein of Barnum or Mussolini. “We’re not in bad shape now, but this is no American century.”

Other factors unsettling Trump’s United States are increasingly liberal social changes, such as the growing acceptance of same-sex marriage and the rise of political correctness, and the changing ethnic make-up of the country. In 1965, 84 per cent of Americans were non-Hispanic whites. By 2015 this had fallen to 62 per cent. Nationally, Hispanics make up about 15 per cent of the population; they will make up 25 per cent in 2044, according to William Frey, a demographer at Brookings. This will turn the US into “a majority minority” nation: its white population will no longer be in majority.

“If the economy were doing better and if the culture weren’t changing so fast, there would be more light and less heat over immigration policy,” says Galston. The influx of nearly 59 million immigrants over the past half-century and the estimated 11 million unauthorised immigrants living in the US have made them popular targets of anger over the loss of American jobs. Trump has promised as president to deport all illegal immigrants.

"Everybody in America loves immigration – as long as it came two generations back," says Daniels, who is also the author of Guarding the Golden Door, a 2004 book on American immigration policy. He points out that Irish, Germans and Italians were ostracised by US society before being accepted. "I don't think immigration has played this big a role in any major campaign prior to this year," he says.

Political polarisation

Polarisation in politics has also fuelled Trump’s rise. The decline both of the southern conservative Democrats who helped Reagan pass Bills in the 1980s and of northern liberal Republicans has added to Washington gridlock and stirred the political elite’s approval ratings to record lows.

Democrats and Republicans have largely migrated towards their ideological flanks on the left and the right. Pew Research found in 1994 that 23 per cent of Republicans were more liberal than the average Democrat and that 17 per cent of Democrats were more conservative than the average Republican. Today those figures are 4 per cent and 5 per cent. “The US is really between a rock and a hard place. It is fading into a lot of the frustration because the country is pretty evenly divided,” says Poole.

Trump’s “coalition of the angry” is composed not only of conservatives who never accepted Obama’s presidency but also of voters who feel betrayed by Republicans. The party, they believe, failed to deliver on its promises after it regained the House of Representatives in the “Tea Party wave” of the 2010 midterm elections and, four years later, when it added control of the Senate.

Almost six in 10 Republicans in Georgia and Alabama said in exit polls that they felt betrayed by their party, as did about half in Virginia, scene of Trump’s fierce rally last Monday. “There is this pervasive sense of betrayal, and the narrative is that if we had had tougher leaders then we would have accomplished our objectives,” says Galston. “It is easy for people representing themselves as tough new leaders to piggyback on that sentiment.”

Less than half

Donald Trump has ridden far and wide on that anger. It is felt by northern blue-collar workers and by southern evangelical Christians. The large field of Republican candidates has meant that he has won 10 states without taking more than 50 per cent of the voters in a single one of them. He won three states – South Carolina, Arkansas and Vermont – with just a third of the vote.

Anger has put him in the lead in the Republican presidential race, but could it put him in the White House? Hillary Clinton, the expected Democratic nominee, has led Trump by single digits in all but one poll over the past month, suggesting a head-to-head battle between them.

Galston raises the phenomenon of the “October surprise” in the month leading to the election that could further upend this topsy-turvy election. “Let’s say Clinton has a nine- or 10-point lead at the beginning of October,” he says. “Then there is a major terrorist event: Isis gets a vote. I can think of all sorts of reasons why they would just love to have someone with Mr Trump’s declared positions on Muslims in the Oval Office. And if there is a security panic in the months before the election, frankly all bets are off. I don’t know what would happen under those circumstances.”

This imponderable, Galston says, could produce the nastiest October surprise ever.