On the morning of the Iowa caucuses, the first contest in the presidential nominating process, I went to a high school in West Des Moines where some of the Republican candidates were addressing students old enough to vote this year. The students gave perfunctory applause to two of the candidates and four of the front-runner Mitt Romney's rock-jawed sons. Then a roar went up from the bleachers. From where I was standing, all I could see was a scrum of people and cameras moving slowly across the floor but I knew that only one person in the underwhelming 2012 Republican field could cause such excitement. The scrum reached the riser set up in front of the bleachers and there he was - a very slight, stooped old man with wispy grey hair and jutting ears, wearing a black shirt and looking for all the world like an ageing member of a country music band on a final reunion tour.
But no, this 76-year-old was an obstetrician-turned-congressman, who then embarked on a ramble through his doctrine of "true liberty" - strict constitutionalism, "sound money", guarding against tyranny. The students sat transfixed and roared again when he left.
I asked one, an 18-year-old with long brown hair, why she was cheering. "Ron Paul is the one who took us seriously," she said. "He actually talked to us about his plans - he talked to us as adults, not as children."
Outside, I watched as the scrum swept Paul to his SUV, a beefy bodyguard at his back. Nearby, dozens of Paul supporters, most of whom had travelled from other states, were chanting and waving signs. Reporters in the maw shouted questions at him but he simply smiled and shuffled along. As he reached the vehicle, one of the reporters shouted in exasperation: "Are you not going to answer any questions or is that just being Ron Paul?"
Being Ron Paul, it turns out, was enough to set off the most remarkable movement around a single political figure that the United States has seen in at least a decade, other than the one that Barack Obama inspired in 2008 and is fighting desperately to revive. Paul had built up a loyal but limited cadre of supporters through his decades as a libertarian agitator both inside and outside Congress, where he has established himself as the "Dr No" who votes against just about every spending bill that comes along.
He started reaching a broader audience with his 2008 run for the Republican nomination when, quivering in his ill-fitting suit, he stood up for his anti-interventionist foreign policy views against the bullying scorn of the other, uniformly hawkish candidates, most notably the former New York mayor Rudy Giuliani. ("They attack us because we've been over there," Paul said in describing his "blowback" explanation for the 11 September 2001 attacks.) He raised serious money and attracted a crew of travelling fans so devoted that aides had to discourage them from attending events to make sure undecided voters could see him.
This time, he's back again in what could be a last hurrah, as he has decided to give up his congressional seat for Texas this year. And he's drawing even bigger crowds and having more of an impact at the polls - he won 21 per cent in Iowa, just behind the ex-moderate quarter-billionaire businessman Romney and the former Pennsylvania senator Rick Santorum, a socially conservative hawk. Paul then took second place behind Romney in the next nominating state, New Hampshire. If Romney does not run away with the nomination - as he appears to be poised to do, given his enormous resources and the inexplicably weak field - it is conceivable that Paul could leverage his delegates into a role at the Republican convention next summer, after years of being treated like a crazy uncle by the party.
In a sense, it doesn't really matter how well Paul performs in the upcoming contests, because his victory is already in hand. After several weeks on the campaign trail, I have been startled to see confirmed what I was already picking up in Washington and from the candidates' televised debates: the Republican Party now sounds an awful lot like Ron Paul. Not on foreign policy, to be sure, though another GOP candidate, the former Utah governor and ambassador to China Jon Huntsman, Jr, has taken a bring-the-troops-home line as well. Paul still tangles plenty with the other candidates over Iran ("They don't threaten our national security") and Israel ("They're quite capable of taking care of themselves"). Yet the rest of the Paul package - the profoundly anti-government rhetoric, the call for states' rights and the doomsday warnings about the federal debt - is now popping up in the stump speeches of even Milquetoast establishment Republicans such as Romney. This is not Paul's doing alone - the Tea Party movement that arose in resistance to Obama can also take credit. But if there is a single person most responsible for the apocalyptic, anti-government outlook that has overtaken American conservatism, it is Paul. As the journalist David Weigel, a long-time Paul observer, put it, he is "arguably the most intellectually influential member of the House of Representatives in a generation".
This is particularly remarkable given Paul's circuitous route to Washington. Raised on a dairy farm outside Pittsburgh, he worked on a milk delivery route from an early age, excelled at sport and married the daughter of a wealthy coffee broker. After medical school, he was drafted into the air force as a flight surgeon and afterwards settled on the Texas Gulf Coast, where he set up an obstetrics practice. He delivered more than 4,000 babies and always refused to accept as payment Medicare or Medicaid, the two government-run health programmes. On the side, he read heavily in the Austrian school of free-market economics - Friedrich Hayek, Ludwig von Mises et al - and when, in 1971, Richard Nixon took the dollar off the gold standard, Paul joined the fray on behalf of sound money. (He has put his money where his mouth is and holds several million dollars' worth of stocks in precious metals.)
He lost his first run for Congress in 1974, won a special election in 1976, lost again that November and then made it back in for three terms. After losing a Senate primary in 1984, he returned to obstetrics. His cause carried on, however, with a 1988 presidential campaign on the Libertarian ticket (he won 0.5 per cent of the vote) and in the form of newsletters with titles such as The Ron Paul Survival Report that, it emerged, were riddled with racist, pro-militia and anti-Semitic commentary. (Just one of many examples, referring to the Los Angeles race riots of 1992: "Order was only restored in LA when it came time for the blacks to pick up their welfare cheques.")
Paul has said that he did not write the newsletters and learned of their content only years later. His favourite defence against charges of racism is to point out that he wants to do away with the drug laws that imprison black men at vastly disproportionate rates. At the same time, he sees the Civil Rights Act as a federal overreach and argues that the civil war was unnecessary - the North should simply have paid the South for the slaves' freedom.He made his return to the Congress in 1996, where he resumed his Dr No routine, calling for the end of the Federal Reserve and opposing even spending on disaster relief and farm subsidies that his rural, hurricane-prone district depends on. He sponsored hundreds of bills, virtually none of which made it to the floor for a vote. But after his 2008 run and the financial collapse, the anti-bailout anger that helped spawn the Tea Party also gave Paul new cachet in Washington. Conservative House Republicans flocked to his weekly policy luncheons. In December 2010, he was handed the chairmanship of the subcommittee overseeing monetary policy and, a few months later, he got all House Republicans to vote for his bill to audit the Federal Reserve. Meanwhile, his sway was growing outside Washington - Youth for Ron Paul chapters proliferated on college campuses and it was easy to see an overlap between the Paul camp and the anti-bailout, anti-military- industrial-complex rhetoric of the Occupy Wall Street movement.
What are we to make of all this? There have been isolationist and conspiratorial strains in US politics since the earliest days - what the historian Richard Hofstadter in 1964 labelled the "paranoid style". Yet Paul's popularity has reached the point now where it must be reckoned with; for just about every slice of the political spectrum, there is some element of the Paul movement that produces discomfort. For Republicans, the indictment is plain. At a time when the other candidates take pains to avoid any mention of George W Bush, Paul harps on about the failures of the Bush years - from the war in Iraq (Paul was one of the six House Republicans to vote against it) and spending on things such as a new Medicare prescription drug entitlement. He rankles the neoconservatives by denouncing the human and fiscal costs of intervention more explicitly than any Democrat, decrying their lust for "empire" and going so far as to label as "chicken hawks" Republicans who support war without having served in the military themselves. And his ideological consistency (which is marred by his anti-abortion views) is a challenge to the Tea Party movement, whose anti-government sentiment is often selective.
Democrats and liberals, too, must reckon with him. For a start, his legions of young followers are evidence that there are plenty of disaffected young people, whom he is leading as effectively as Obama did in 2008, albeit in an entirely different direction. Liberals must also grapple with their mixed feelings about Paul - cheering on his anti-hawkish declarations while shuddering at the rest. Can they have one without the other, or should they scrutinise more carefully the half they find acceptable? Most of all, liberals must contend with the influence of Paul's anti-government rhetoric. Now that more mainstream Republicans are talking about shutting down federal agencies, eviscerating regulations and slashing taxes, the time has come for a full-throated counter-argument explaining to voters what Paul's America would really look like.
The more immediate implication of Paul's political rise is the potential for a third-party candidacy on autumn's presidential ballot. Paul has played coy but Republicans are reassured by the arrival in Washington last year of Kentucky's new senator, Rand Paul, an ophthalmologist who presents his father's ideology in a more burnished package. Establishment Republicans opposed Rand's nomination but are now hopeful that Ron will be sufficiently intent on protecting his son's prospects within the GOP (who knows, maybe a real run for president?) that he will not risk hurting the party's chances with a third-party run this year.
Clean bill of health
For now, though, Ron Paul simply keeps on being Ron Paul, a kindly, hard-of-hearing great-grandfather, traipsing around the country selling his ideas as cheerily as he and his wife have for years distributed their family cookbook. The other day, I ventured up to the New Hampshire lakes region, where hundreds had descended on a lakeside hotel to see Paul speak in a salmon-coloured ballroom. It was the usual circus - anti-Zionist rabbis holding signs outside, foreign tourists who had come to see the famous man, young people with T-shirt slogans such as: "When fascism goes to sleep, it looks under the bed for Ron Paul".
Standing in front of the room in a grey sweater, Paul made his case for reviving the economy by "letting the bad debt be liquidated" and ending the federal income tax: "If we didn't have the income tax, then everyone would have more money to spend." Challenged by a New York police officer, he stuck by his opposition to any Middle East intervention: "How would we react if that was done to us?" Asked by a man with an ailing teenage daughter what would happen to her after Paul eliminated health insurance regulations, he promised that the liberated free market would provide for her care.
Afterwards, he held a press conference in the ballroom, with his supporters still hanging on the fringes, cheering his answers. A reporter asked about his health, given that he has been taking more breaks from the trail than other candidates. "My health? Let's go for a bicycle ride!" Paul said to the young woman. "I feel very good. Your health depends on your mental status, as well. I feel excellent."
For Dr Paul, the self-examination apparently reveals a mind that's thinking clearly as can be. For a country in which his brand of extremism is gaining such currency, the self-diagnosis is surely more dire.
Alec MacGillis is a senior editor at the New Republic