"Freedom is a young idea," he told PBS Newshour in July.
"It's only been tested for a couple hundred years. And we had a taste of it and we're throwing it away."
Far from being too old - a frequent jibe from media pundits - he insists his rivals have "old ideas" and that by championing liberty he challenges a reactionary status quo.
He cites the Patriot Act, a draconian touchstone for conservatives in the "War on Terror", as a prime example of how Washington chips away at civil liberties, a scary thought to his rivals who, unlike Paul, cheered last week's drone-assassination of al-Qaeda propagandist Anwar al-Awlaki.
At a breakfast held by the Christian Science Monitor, Paul excoriated both parties. "They are not talking about what I'm talking about, they are not talking about free market economies, they are not talking about how the middle class gets wiped out, they are not talking about a foreign policy that would defend this country and not pretend that we can police the world forever."
Such sentiments bolster Paul's image as a straight shooter unafraid of special interests.
The 76-year-old congressman from Texas, who sits on the Republican Party's right as a libertarian conservative, has been true to his root-and-branch fiscal philosophy.
He advocates a return to the gold standard, abolished by Richard Nixon in 1971, draconian spending cuts that would gut government agencies, including the military, low taxes, and an end to the Federal Reserve, which he says drives inflation. As Americans rage against corporate greed, and pundits warn the world's economic system is teetering on the verge of collapse, Paul's 2007 warning of impending economic meltdown seems prescient.
Paul, a former doctor, is a loose cannon whose many votes of dissent in the House of Representatives - he advocates strict adherence to the constitution for all laws - earned him the sobriquet: "Dr No." He opposes the war on drugs and made a doomed bid to decriminalise cannabis, co-authored with gay Democrat congressman Barney Frank. And his lonely cry for fiscal rectitude seems prelapsarian to voters aghast at huge public bailouts and the trillion-dollar US deficit.
"In many ways he was the Tea Party before the Tea Party was cool," says Ken Vogel, chief investigative reporter for Politico. Back in his 2008 presidential run Paul - who debuted as congressman in 1976 and voluntarily returned to medicine between 1984 and 1997 - was an almost iconic figure to youthful fans who followed his exploits on YouTube: the guy who wasn't a corporate stooge. Young conservatives coalesced around him.
And while Grand Old Party rivals treat Paul with frosty indifference, his fundraising clout makes the congressman hard to ignore.
In the first half of 2011, his campaign gathered almost US$4.5 million ($5.8 million) and this week announced US$8 million raised in the third quarter. Not up to Mitt Romney and Perry levels - although Paul's 100,000 donors are quintuple Perry's base - but enough to buy more TV ads, stay on the campaign trail, nip at the heels of the two top-tier runners, and continue to spread the word until next August's GOP convention.
"The fact that Paul engaged Rick Perry, who was riding high in the polls, in the cut and thrust of the daily campaign and then in the debates, is proof of his impact," says Vogel. "So Perry, a potential frontrunner, is taking time and bandwidth away from his message to address a guy who four years ago was regarded as something of a kook."
Always a strong performer in straw polls - he placed second, after Michelle Bachmann, in Iowa in August - Paul is doing well nationally. Last month, a Rasmussen poll found, if an election were held then, Paul would reap 38 per cent of votes to Barack Obama's 39 per cent. He placed behind Perry and Romney, but ahead of Bachmann. A CNN poll put him ahead of Bachmann and Sarah Palin.
The big question is if Paul's small government and fiscal discipline mantra will poll well as the race heats up. Does his surge - the Associated Press suggested Paul was "proving to be a force" - really amount to much? Can the candidate who bills himself as "the leading advocate for freedom in our nation's capital", come in from the cold?
Probably not, suggests Larry Sabato, a seasoned observer of presidential contests and head of the University of Virginia's Centre for Politics.
"What you need to understand is that Paul has a ceiling of 20 per cent. He is not going to be the nominee or come anywhere close to being the nominee. There's no chance."
Even his base, says Sabato, accepts this.
"They support him because they believe in his views on the Federal Reserve, or they're glad someone is speaking out against Afghanistan in the Republican Party, or they simply admire the guy's principles. I've seen a lot of young people who are Paulites for many reasons. But this is not a serious movement within the Republican Party. At least not serious enough to come anywhere close to getting a nomination."
Instead, his impact may be in shaping the GOP platform. "If he can demonstrate significant support on the right for a more libertarian perspective, then other GOP candidates will be forced to adapt to that, or at least provide a compelling answer as to why he's wrong," says Vogel.
Paul is stage centre in a seismic struggle between the Old Guard and the Tea Party to recast the GOP as a force for fiscal conservatism, breaking with the social conservatism and national security conservatism that dominated the Bush era.
The lacklustre GOP field and the nation's angry and fearful mood may have given Paul space to push his ideas. But the Tea Party may be ebbing from the high tide reached at last November's seismic mid-terms.
Some say Paul is little more than a spoiler, siphoning votes, air time and money off rivals while his core support is likely a lost cause for other GOP hopefuls.
Ultimately, Paul may become a curious footnote in US presidential history, the lonely voice from the Lone Star state, out of sync with the US political duopoly.
THIRD BID BY AGEING REBEL
This will be Ron Paul's third bid for the White House, after runs in 1988 and 2008.
Conventional wisdom says he is a quixotic oddity, too old for office - he would be 77 if he became President in 2013; Ronald Reagan, the oldest incumbent so far, was just shy of 70 - and handicapped by libertarian beliefs that turn off Middle America. Not too many Baby Boomers warm to Paul's insistence that Medicare and Social Security be hacked back.
Until recently, Paul seemed to operate under the radar. "How did Ron Paul become the 13th floor in a hotel?" asked comedian Jon Stewart, while the Huffington Post quipped he "gets his best coverage from all the coverage covering his lack of coverage".
His age does not help his chances. Neither, arguably, do his ideas, which threaten a political status quo dominated by a duopoly resistant to real change. But Paul refuses to fade away, gaining leverage as the Tea Party's muse. While Michele Bachmann, Sarah Palin and Rick Perry tried to exploit the movement's grassroots fury, Paul is the real deal.
Amazingly, it takes a septuagenarian to emerge as a rebel, happy to end the "insane" war in Afghanistan - he opposes military adventures - dump the CIA and vanquish one federal agency after another.
