The crowd strained forward as the lights dimmed, a sea of smartphones trained on the stage. Whoops and cheers turned to screams of delight as a gaunt-looking figure mounted the steps and slowly approached the microphone.

This wasn't a rock star or the latest teen idol as you might have expected from the almost universally young gathering. This was 76-year-old Ron Paul, the spidery libertarian from Texas, shuffling towards the podium, his shoulders hunched, head bowed, eyes squinting in the spotlight.

"President Paul! President Paul!" came the chants as he peered out at 500 supporters crammed into a hot, sweaty New Hampshire function room. It was election night in New Hampshire and Paul was celebrating an achievement he has worked for tirelessly for almost 25 years. He had finally secured a seat at the high table of presidential hopefuls by coming in a solid second – a feat that had eluded him in two previous runs for the White House.

So how would he mark this turning point: would he deliver a tub-thumping call to arms in the mould of Teddy Roosevelt? Or would he be smoothly triumphant like Ronald Reagan?

Neither, as it happened. "I think you know my wife Carol," he said, voice trailing off from the microphone.

That's the thing about Paul: he never plays by the book. While his rivals for the Republican nomination – frontrunner Mitt Romney, Newt Gingrich, Rick Perry and Rick Santorum – repetitively recite rehashed speeches full of TV-friendly soundbites, Paul takes his fans on an intellectual rollercoaster ride that is never predictable. He might begin with a call for an end to all foreign wars, segue to demand the legalisation of drugs, throw in a defence of WikiLeaks and end with a detailed economic discourse on why the Federal Reserve must be abolished and replaced by the gold standard.

It's an unlikely formula, but one that has earned him a growing army of ardent followers, many aged under 25, across an astonishingly diverse set of political camps. His rallies are attended by anti-war veterans in uniform, religious conservatives, legalise cannabis campaigners, home schoolers, Truthers, anti-abortionists … Kelly Clarkson, an American Idol winner, backs him while the late Timothy Leary, champion of all things psychedelic, once threw a fundraiser for him.

Lew Moore, national campaign manager for Paul's bid for the Republican nomination in 2008, spent a year at his side and watched his support base grow exponentially. "We were starting from scratch – there was no Ron Paul movement in 2007 – and it was mind-blowing to see how quickly it exploded," he says.

Moore, who now works as a consultant, puts Paul's success partly down to the fact that voters think he is genuine. "He doesn't deal in cute soundbites or deliver stump speeches. His idea of preparing for a speech is to write three words on an envelope and then go out there and talk for 50 minutes."

Manifesto

In his 2008 book, The Revolution: a Manifesto, Paul admits that when friends first urged him to run for the presidency in 2006 he was reluctant, and was "not at all convinced that a sizable enough national constituency existed" for him. Those doubts were squashed in New Hampshire on 10 January, where he took 23% of the votes, behind Romney's commanding 39% but far ahead of the rest of the field. Exit polls suggest that fully half of the 18- to 29-year-old voters chose Paul.

"This is his moment," says Bruce Buchanan, an expert in presidential politics at the University of Texas at Austin. "He speaks to a restive country that is anxious about the economy and sceptical of government intervention at home and abroad. And in the process, he's redefining the Republican party."

Ronald Paul was born on 20 August 1935 and raised in a small town in western Pennsylvania, where his father ran a dairy company. His family was strictly Lutheran; two of his brothers became church ministers. After school he went into medicine, then into the air force – serving as a flight surgeon – before settling as a doctor in 1968 in Texas where he had been stationed. As an obstetrician, he famously delivered more than 4,000 babies.

Religious conviction runs through his second career as a member of the House of Representatives, where he sat from 1979 to 1985 and again since 1997. For instance, he opposes the federal right to an abortion in Roe v Wade.

But faith only goes so far in explaining his highly individual philosophy. Equally important has been his wide and varied reading, beginning with the two bedrocks of his thinking: the US constitution and the Austrian school of conservative economists, Friedrich Hayek and Ludwig von Mises.

They provide the foundations of his core beliefs in small government, free markets and individual freedom. Paul also draws on a bewildering array of sources to inform his thinking. In Revolution he quotes from Augustine and Thomas Aquinas, John Quincy Adams and Robert Taft, Bertrand Russell, Frédéric Bastiat and the Salon columnist Glenn Greenwald among many others.

This is not done for show. Paul is as much a public intellectual as he is a politician. "Politicians don't amount to much," he once said, "but ideas do."

He has shown himself consistently unwilling to bend his beliefs in favour of political expediency, even where that leaves him alone and in the wilderness, earning himself the moniker "Dr No" in Congress. Most notably, he has stood doggedly against US military interventionism around the world. He was one of only six Republicans to vote against the 2002 congressional resolution paving the way for the Iraq invasion and has called for all American troops to come home.

At the most recent Republican TV debate in Myrtle Beach, South Carolina, on Monday night, Paul even defended his position that the killing of Osama bin Laden was against international law. "What's wrong with capturing people? There are other ways of doing this. Think of Saddam Hussein – we captured him" he said, adding that if a Chinese dissident found asylum in the US "we wouldn't endorse the idea [the Chinese] can come over here and bomb us".

It was a particularly brave – or rash – thing to say given that South Carolina is one of the most heavily militarised states in America and is peppered with military bases . Sure enough, the rowdy crowd in the Fox News audience gave him a lusty boo - the loudest of a rambunctious night and maybe of the entire primary season so far - while Gingrich called him "utterly irrational" for questioning the manner of Bin Laden's killing.

His anti-Iraq war stance, as well as his opposition to the Patriot Act and the use of torture on terror suspects, have gained him some strange bedfellows. Dennis Kucinich, leftwing Democratic representative in Ohio, is a Paul admirer.

Kucinich says: "I've worked with Ron Paul and I know he cannot be bought, cannot be bossed around, keeps his own counsel and is a person of conscience. He's shown a lot of courage in challenging three wars – the war on drugs, the war on civil liberties and the wars America prosecutes around the world."

One of the most conservative voices in Congress stands hand in glove with one of the most liberal. Such unconventional alliances are another element of Paul's attraction to his army of young supporters, who are scathing of the horse-trading that goes on within and between the two main parties. As Nick Brancato, 31, said as he stood outside a New Hampshire polling station on the day of the primary: "He's the only candidate who makes sense and wants change. He doesn't flipflop, he's always said what he believes in and I know he's not going to change his stance when he's elected."

Jason Alan, 36, travelled to New Hampshire from Ohio to lend Paul a hand. "It's the whole package, the fact Ron Paul has been around for 12 terms and never taken lobbyists' money," he said.

His friend Andrew Moson, 27, who owns a concrete grinding firm in Cleveland, Ohio, said Paul had taught him to think critically. "The stuff he says you don't hear anywhere – not from parents, teachers, the news media."

Yet Paul remains at heart an ultra-conservative guided by a rigid dislike of government, who shares many of the convictions of the Tea Parties that he has in turn inspired. A Paul presidency would seek to abolish the education department (hence the home schoolers among his fans), end all federal controls on pollution, eliminate income tax, cut public spending by $1 trillion (£650bn) in year one and transfer most powers from Washington to individual states.

Many of those policies fall under the umbrella of "libertarianism", but even libertarians are baffled by some of his ideas. Paul proposes free trade, but has voted against free trade agreements such as Nafta. He calls for government to stop interfering in people's private lives, but introduced a bill into Congress that would define life as beginning at conception – and supported the building of a fence along the border with Mexico to deter immigrants. "Some of his positions make an awkward fit with standard libertarian views," says Jeffrey Miron, a Harvard economist and author of Libertarianism, from A to Z.

Race

A similar awkwardness has been attached to his views on race. He presents himself as a committed anti-racist, insisting that any notion of racial superiority is anathema to his belief in individualism. But he has struggled for years to shrug off controversy surrounding newsletters published during the 1980s and 90s bearing his name. The Ron Paul Political Report and other publications carried an article titled The Coming Race War and a piece on the Washington black riots headlined Animals Take Over the DC Zoo.

Paul has said the newsletters were not edited or written by him, though he accepts he should have paid "closer attention". But his refusal to name the author of the ugly articles has left a sour smell in the air.

Paul may not do brilliantly in the primary in South Carolina given the booing we heard on Monday night. But, like the race row, a poor showing this weekend is unlikely to stop him now. He already has enough fuel in his engine – both cash and political energy – to carry him through the primary season long after other candidates have dropped off. He has already outlived John Huntsman, Obama's former ambassador to China, who crashed out of the race on Monday, and others are likely soon to follow suit.

Few observers expect Paul to beat the frontrunner, Romney, but he could continue to be a force to reckon with right up to the Republican convention in Tampa Bay, Florida in August.

The nightmare scenario for the Republican establishment would be him running against Romney and Obama as a third-party candidate in the presidential election itself. That's not a ridiculous thought. After all, he's done it before, having stood for the Libertarian party in 1988. And he's shown repeatedly that loyalty to his party is not what drives him. So would he do it? Would Paul have the gall to run against Romney, knowing it might split the conservative vote and hand Obama a second White House term?

"It depends how the Republican party treats him between now and August," Buchanan says. "This would be his ace in the hole, and it's what the Republican leadership fears most."

Pocket profile



Born 20 August 1935

Age 76

Career Flight surgeon in the US air force, followed by a career as an obstetrician before he moved into politics. He represented the 22nd district of Texas in the House of Representatives from 1979 until 1985, went back to practising medicine until 1997 and from 1997 has represented Texas's 14th district.

High point December 16 2007 Paul held a "moneybomb", the internet fundraising blitz pioneered by his supporters, on the anniversary of the Boston Tea Party and brought in $6m in 24 hours.

Low point June 1992 A supplement to the Ron Paul Political Report titled Special Issue on Racial Terrorism said: "Order was only restored in LA when it came time for the blacks to pick up their welfare checks." Paul insists he did not write or edit the supplement.

What he says "I have to chuckle when they describe me as 'dangerous'. This time they are telling the truth, because we are dangerous to the status quo."

What they say "You are an enigma wrapped in a riddle nestled in a sesame seed bun of mystery" – Stephen Colbert