Donald Trump predicted on Friday afternoon that he will score a mind-blowing election victory on November 8 similar to the June 23 'Brexit' vote that set Great Britain on a course to leave the European Union.

'We will win. We will shock the world,' he pledged in Johnstown, Pennsylvania, a decaying steel town of the sort that is tailor-made for Trump's populist, job-saving message.'

'This is going to be Brexit-plus. Brexit-plus,' he said. 'And a lot of people know it.'

During an earlier rally near Asheville, North Carolina, he described it as 'Beyond Brexit.' Later at night he would settle on 'Brexit times five.'

The Republican presidential nominee told an audience estimated at 5,000 in Johnstown that a craven, dishonest mass media is masking the size and intensity of the political movement he has created out of thin air.

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Republican presidential nominee Donald Trump held a Friday afternoon rally in Johnstown, Pennsylvania, joking that a rain shower got his hair wet

The Republican presidential nominee predicted a 'Brexit-plus' victory similar to the world-shocking result of June's British vote to leave the European Union

'This is a movement like has never taken place in our country before. And the dishonest media doesn't like talking about our movement. They don't like talking about it,' he lamented, as boos rained down on reporters.

Trump is trailing Democrat Hillary Clinton in a majority of opinion surveys. But his Brexit reference hints at a potential come-from-behind win that would confound pollsters and America's political class.

Oddsmakers in Europe report that nearly three-quarters of the money being bet on the election is staked on Clinton. But Trump-backers are placing a large majority of the bets, albeit in smaller amounts of money.

The same phenomenon was seen before the Brexit vote. The result shocked the world.

The Trump campaign is depending on a groundswell of voters who are invisible to pollsters, either because they recently registered for the first time in their lives or because they are sheepish about telling a live interviewer that they ride the Trump train.

In some parts of America where Democratic voters outstrip Republicans, being outwardly pro-Trump can fall somewhere along the spectrum between unfashionable and a hanging offense.

For that reason, Republicans look hopefully at data showing more Trump supporters when voters answer surveys anonymously instead of talking to another person.

Trump marveled at his treatment by the 'dishonest' press corps including some reporters whom Hillary Clinton's campaign sees as 'friendly and malleable'

It remains to be seen if any such phenomenon might be sufficient to swing enough electoral votes in Trump's direction.

But a similar fluke plagued pollsters before the Brexit vote: Surveys showed voters rejecting the separatist referendum by 18 percentage points.

It didn't turn out that way, and Trump believes he's riding the crest of a similar wave.

The sea of humanity that met Trump in Johnstown, like most of his crowds, laughed along with his jokes and booed the media when he castigated them.

They also chanted 'Drain The Swamp!' before he arrived – the first such appearance of Trump's newest anti-establishment slogan.

After jockeying for position as campaign aides flung hats and fired a ti-shirt cannon into the crowd, they were tuned in to their hero's every word.

Trump at one point cast Clinton as a career politician who operates without a public or private conscience.

'She lied over and over and over and over,' he exclaimed, as the audience joined him on the third 'over.'

Trump said his movement will 'shock the world' on November 8 with an unexpected victory

They picked up the ball and ran with it after Trump stopped, continuing en masse: 'and over and over and over and over and over!'

Trump pitted his devotees against the press in new ways on Friday, promising to keep secret his strategy for defeating the ISIS terror army until he executes it.

'"But Mr Trump," he said, mimicking a journalist in mid-interview. '"The American people demand to know".'

'They don't! he yelled. 'The reporters demand to know! They're the only ones!'

Trump also used a recent WikiLeaks disclosure as a cudgel to beat up a New York Times reporter who has covered both his campaign and Clinton's.

'WikiLeaks also shows in new emails the Clinton campaign boasting about working with – quote – "very friendly and malleable reporters," including a reporter from The New York Times they described as "safe",' he said.

'I have that same reporter. She's not safe! She's brutal on us. I wish my people would say, "She's safe! Oh, she's safe!" meaning she'll do whatever the hell they want her to do.'

'We are in a rigged system,' Trump said, returning to one of his broader themes, 'and a big part of the rigging are these dishonest people in the media. Big part. Big part of it.'

The boo-birds came back with a vengeance as he painted reporters as adversaries to everyone in the arena.

'Isn't it amazing how – you know, they don't even want to look at you, folks! I think they consider you, like Hillary, they consider you deplorable. And irredeemable also!'

'The media, the special interests, Wall Street, the career politicians – the system is rigged,' he said.