CONCORD, N.H. — Ron Paul's Granite State campaign headquarters is hidden in an industrial park and would be virtually impossible to find but for the gaggle of 20-somethings smoking outside.
Step inside and you hear the buzz of activity — until an anxious campaign staffer acts like you've infiltrated Fort Knox and sends you away.
This is a grass roots movement with a stealth operation working overtime not just in New Hampshire but in more than a dozen other states largely ignored by the rest of the Republican presidential field.
Its grandfatherly standard-bearer, the 76-year-old Texas congressman and retired doctor, is a long shot to win the nomination. But he's well funded and well organized and has a vast base of support that the GOP dismisses at its own peril.
"I've always voted Republican, but right now I would consider voting for an independent candidate," engineer Al Garnett said Friday while waiting for Paul to address a packed airplane hangar in Nashua.
Unlike most of the field scrambling to gain traction in New Hampshire on Tuesday, South Carolina on Jan. 21 and Florida on Jan. 31, Paul's campaign is preparing for a long slog well into the spring, raising $13 million over the past three months. Several states hold caucuses in February, which can be particularly fertile for a well-organized grass roots campaign like Paul's.
"Ron Paul and Mitt Romney are going to be the last candidates standing because they're the only candidates who are likely to have money to keep going,'' said Osceola Republican state committeeman Mark Cross, who is leading Paul's campaign effort in Florida.
While much of the GOP establishment casts him as a cranky gadfly, Paul has the potential to build up a significant number of delegates and a base of support to, at the very least, demand a high-profile speaking slot when Republicans crown their nominee at the Tampa Bay Times Forum in August.
"Absolutely he should,'' Republican engineer Jeff Creem of Nashua said. "If they don't do that, it would basically be a sign that they're completely taking us for granted."
Paul finished a disappointing third in the Iowa caucuses this week, and recent polls put him a distant second behind Romney in New Hampshire. The candidate who calls for ending all foreign entanglements and for draconian cuts to the federal budget appears to have a ceiling of support among Republican voters, but he's also a top-tier contender.
"They call us dangerous,'' Paul told roaring supporters Friday. "In a way, we are — to their empire. We're dangerous to the special interests and the big spenders."
Paul is the only Republican candidate who attracts many young voters, and his crowds tend to be far more energetic than his rivals'.
"If Republicans are going to have a chance, they're going to have to reunite somehow these young people who bring a lot of energy to the GOP,'' said University of Virginia political scientist Larry Sabato.
Many of his students are Paul supporters who care deeply about deficit spending but not social issues like gay marriage, he said.
In Nashua on Friday, Paul scoffed at critics who deride his foreign policy as dangerous or out of the mainstream.
"Oh, yeah, very strange: strong national defense. Mind your own business. And take care of ourselves,'' the candidate said amid "President Paul! President Paul!" cheers. "Minding your own business is a much better way to get along with people than dropping bombs on them."
As much as Paul may crimp messages the GOP wants to convey during the national convention in Tampa, the party may have to do all it can to avoid antagonizing him. He says he has no plans to launch a third-party campaign, but he hasn't ruled it out either.
"They can survive an hourlong speech,'' Sabato said. "What they can't survive is having him bolt."
The winner of Florida's primary will win all its 50 delegates, which makes it a big hurdle for Paul, whose supporters are still organizing aggressively and aiming for a solid showing.
"Mitt Romney doesn't have a base of people who love him and respect him and are eagerly walking and knocking on doors for him. Ron Paul has that in spades,'' said Paul's main Tampa Bay organizer, Alex Snitker, who noted that 1,400 people have signed up as volunteers in Hillsborough, Pasco and Pinellas counties.
Paul recently won a Pasco GOP straw poll, though some Republican professionals say such shows of support mean little.
"College guys with bad haircuts and Ayn Rand back tats show up, game a straw poll for DOCTOR Paul, then disappear," scoffed Republican consultant Rick Wilson in an email.
That's the sort of assessment the GOP establishment could come to regret.
"The establishment machine, they're completely dissing Ron Paul. They're doing all they can to discredit him. They don't like him, they don't like his policies and they don't like his supporters," Snitker said. "They're going to damage themselves if they're not careful, and don't blame us if (President Barack) Obama winds up winning the election."
Adam C. Smith can be reached at email@example.com.