Des Moines, Iowa: At her campaign launch in New York last month Hillary Clinton appeared polished and implacable, engaged but not engaging. At his in Miami, Jeb Bush looked better than he had in earlier appearances, but still something was amiss. He has yet to lose a certain flatness.

Last weekend at a rally in smalltown Iowa, Donald Trump looked like he was having an absolute ball. So did his audience.

Trump bounded onstage to the cheers of a full house of around 700 at a high school auditorium. Another 500 or so were watching from a nearby overflow room. Outside campaign staff were signing up volunteers, handing out "Trump for Veterans" placards and pulled pork sandwiches and hot dogs and giant gooey chocolate chip cookies.

All this in Oskaloosa, population 11,000, over an hour's drive through corn and soya bean fields from the state capital, Des Moines.

He was introduced by a veteran of his TV show The Apprentice, who described him as "the most brilliant man I have ever met … He thinks about work while other people talk about work."

(Who this leaves to actually do the work was not made clear.)

The moment Trump arrived on stage he started taking shots. "The Des Moines Register is standing outside, too," he began and immediately his pliant audience howled and hissed as though Captain Hook had just appeared in a Christmas pantomime.

And then the Trump show begins. He rambles and boasts and attacks in a speech that keeps going around and around in circles.

"I wrote all this down," he explains at one point, "But I don't have to look at it because I have a really good memory."

The key points are this: Trump is "really smart". Other politicians are "dumb", except for those who lead competitor nations - they are clever. That's why America needs Trump.

Trump is also really rich, he explains, which frees him from the cronyism that has infected American politics.

The Register had been in Trump's sights during the Iowa rally because a few days earlier it had called him a "feckless blowhard" in an editorial and urged him to quit the race.

But there is no sign of Trump quitting, despite the contempt of much of America's media and commentariat, and despite the slagheaps of ugly Trump factoids that are being dumped on front pages daily.

A selection from this week alone: One of Trump's former wives once accused him of rape. Trump's lawyer does not believe rape in marriage exists. Trump once lost his temper in court when a lawyer needed a break to express milk for her infant. He called her "disgusting". Trump's sons like shooting animals for fun, posing for pictures with their slaughtered big game trophies.

And still Trump's poll numbers climb, just as they did after he attacked Senator John McCain's heroic Vietnam War service, just as they did after he described Mexican immigrants as rapists and criminals in his campaign launch.

This week the respected Quinnipiac poll found that he had 19.8 per cent support among likely Republican voters, 6.2 percentage points up on his nearest rival, Wisconsin governor Scott Walker. Another poll had him beating the party's establishment favourite, Jeb Bush, in Bush's home state of Florida.

And though it is months before the first primary competitions, Trump's numbers have significance because they have ensured him a spot in the first Republican debate, to be hosted by Fox News next week.

Because the field was so big, Fox has decreed that only the 10 leading candidates may participate. Trump will now not only be there, but be centre stage, and at the expense of one of the party's leading figures.

Better in person

Trump, the reality TV star and real estate developer, is so dominant in the broad GOP primary field at present that the easiest way to understand the other candidates is to consider their campaigns in comparison to Trump's.

Those who have not made the cut for the debate speak of little else but Trump, with senator Lindsay Graham and former Texas governor Rick Perry leading the charge in direct attacks on him. They do this because they know that discussing Trump is the only way for them to break into news coverage.

Similarly the former Arkansas governor, Mike Huckabee, a Christian right candidate, has had to ramp up his rhetoric to cut through the Trump noise in the media.

"He will take the Israelis and march them to the door of the oven," he said of US President Barack Obama's Iran nuclear deal in an interview last Saturday.

Senator Ted Cruz, another Tea Party candidate, is taking care not to attack Trump and not to offend his base. This is because he believes he might inherit it when Trump finally flames out.

The other frontrunners, Bush and Walker, are - mostly - keeping their counsel, knowing there is no upside for them in getting into a dispute with Trump, and that any attack on him simply increases his stature among the disaffected voters who support him.

From a distance it can be hard to understand Trump's appeal. He appears unable to stick to any line of argument – or even of thought – for more than a few words. It's difficult to quote him in print because his sentences are often so disjointed.

But in his presence, his appeal makes more sense.

A Trump speech resembles an old vaudeville act more than it does modern political rhetoric, and while he jumps from thought to thought, he has a good sense of timing and is often truly funny.

His ideas are simple, and common to most populist politicians: foreigners are taking your jobs, immigrants are dangerous, things were better in the past and I can make them better again.

But Trump gives them his own spin. Constantly declaring how rich he is might be boastful, but the pursuit of wealth is no sin in the US, particularly among Republicans.

And for years the GOP has been telling its supporters that the sole role of politicians is to get out of the way and let the free market take care of the world.

Trump is now telling them not just that he is going to get out of the free market's way, but that he is the free market personified.

"Our country needs, our country needs a truly great leader and we need a truly great leader now," he said during his announcement speech in the lobby of one of his New York towers. "We need a leader that wrote The Art of the Deal (Trump's own 1987 bestseller)."

Further, he contends that his vast wealth frees him of the dictates of the donor class that has become central to American politics. That's not a bad argument.

And as a rank populist, he has freed himself of the bounds of consistency. He declares himself a free marketeer but he promises to slap massive import duties on cars built in Mexico.

He has also declared that unlike other Republican candidates, he would not cut health programs to the aged, nor social security.

As rabble rouser-in-chief for the Obama "birther" movement, Trump demanded the President release his birth certificate, and when that was done, his college transcripts.

He refuses to release his own, despite reassuring audiences that: "I went to the Wharton School of Business. I'm, like, a really smart person."

He has even been able to harness the clumsiness of his language.

Every person who Fairfax Media spoke to at Trump's rally last weekend volunteered that what they liked about him most was that he spoke his mind and did not sound like other politicians.

And it's true. His stump speech is far more interesting to watch than those of his competitors.

Even military veterans forgave him for his attack on McCain, some on the grounds that "McCain started it" (McCain called Trump supporters "crazies"), others because, well, that's just how The Donald speaks.

"He tells the truth," says 76-year-old Dick Thornton, who has just signed on as a state campaign director in Iowa. "He tells people what they need to hear, not what they want to hear."

"He is serious. People used to have an attitude that he is a clown, but he is serious," he adds.

"I support him 100 per cent," says 69-year-old Jim Hast, a Gulf War veteran. "He says what he says and he means what he says. He is not a politician."

Roger Horn, sitting in the crowd inside with his wife Mary Ann, says the same thing. It is very important to him that Trump is not a politician. He has no problem that he is a real estate developer and TV star though.

Generally Trump supporters are the sort of angry lower-middle class white voters who were devastated by the great recession and feel dislocated by rapidly changing demographics and social norms in America. They are grateful to anyone who can effectively channel that anger.

During his speech Trump does fire off a couple of shots at Hillary Clinton, but mainly he talks about himself and his Republican competitors. And immigrants.

Law-suit happy

The recklessness of this tactic is infuriating the party machine, but it can't silence him for fear of provoking him.

Reince Priebus, the chairman of the Republican National Committee, is treading carefully around Trump.

The RNC is painfully aware that whoever wins the primary is going to need to win more support from Hispanic voters to win the election. Having Trump mouthing off about rapists and border walls is not helping.

Earlier this month, Priebus let it be known that responding to concerns from senior party figures and donors he had called Trump and asked him to tone down his anti-immigrant rhetoric. After that story came out Trump responded with his usual bluster, telling reporters that, yes, the call had taken place, but that rather than chastise him Priebus had called to congratulate him on how well his campaign was going.

Priebus has not responded publicly, and his reticence to engage is being read as evidence of the GOP's fear that if provoked Trump might wreak vengeance on the party by running as an independent.

The thought of it sends chills down Republican spines just as it exhilarates Democrats. There is no knowing how many votes Trump might steal from a Republican candidate if he did so.

And you can see why the RNC fears that Trump might react pugnaciously to attempts to rein him in. For a man who has been treated so kindly by fate – inheriting millions, turning it into billions, dodging the Vietnam war due to a bone spur on a foot, surviving several bankruptcies – Trump has an angry streak.

Trump loves to sue people. A truncated list of targets of his lawsuits includes; a Native American tribe in Connecticut, a small business card shop, both of his ex-wives, one of his ex-wives' publicists, the writer Timothy O'Brien, author of TrumpNation: The Art of Being The Donald, The Chicago Tribune (for suggesting that one of Trump's unbuilt towers might not be the tallest in America when completed), TV station Univision, comedian Bill Maher (for suggesting Trump was an orangutan), television impresario Merv Griffin and a Miss USA contender.

Trump has sued the state of New York (twice), the state of New Jersey and Palm Beach county in Florida. In 2011 Trump sued Scotland when it built a wind farm that Trump believed marred the view from a golf course he constructed. He lost the case.

Trump has also sued an airline, other real estate developers and, in 2014, he sued himself. Trump sued Trump Entertainment Resorts, in which he is a 10 per cent shareholder, to force the company to remove his name from two casinos in Atlantic City, which he said were not meeting his standard for excellence.

Historically a sure-fire way to get sued by Trump has been to question his wealth, which he estimates at around US$10 billion, and which Bloomberg this week, using Trump's own financial records filed in accordance with campaign law, estimated at around $US2.9 billion.

"I'm worth much more than $10 billion," Trump told the Daily Mail reporter in response this week. "I think they're a disgrace. And the next time I see Michael [Bloomberg] I'm not going to be so nice."

And so the Republican contenders wait for Trump campaign to blow out. So far there is no sign of that.

As idiosyncratic as his campaign is, it is not the joke that some have described it as.

Trump has hired experienced campaign staff, headed by a team he poached from Americans For Prosperity, the political organisation backed by the billionaire Koch brothers.

His organisation in crucial states, like New Hampshire and Iowa, appears to be as well funded and well organised as any other.

"They have county chairmen in each county in New Hampshire," Lou Gargiulo, a former member of the state legislature now serving as one of Team Trump's county co-chairs, told the National Journal. "There truly is a very serious Trump campaign in New Hampshire at this point in time."

This is not to say it looks likely that Trump can win the primary, let alone an election. Even as his support surges, his opposition hardens.

A CNN poll last week found only 33 per cent of Americans view Trump favourably, while 58 per cent do not. Trump may lead an overcrowded Republican field of presidential candidates, but nationally he remains the most disliked person in the race, by far.

There is some evidence his campaign is already damaging the Republican Party. A Pew Center poll this month found the GOP is now at historic levels of unpopularity. Only 32 per cent of Americans have a favourable view of the party, the lowest mark ever in that survey.

Sixty per cent of Americans view the Republicans unfavourably - again, the worst score in the party's history.

As long as the Trump show goes on, there is little the party can do but watch and wait, and little the candidates can do but try and work out how to deal with him on the debate stage on August 6.

"Imagine a NASCAR driver mentally preparing for a race knowing one of the drivers will be drunk," observed the Republican strategist John Weaver this week. "That's what prepping for this debate is like."

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