To many of his fellow House Republicans, Rep. Ron Paul (Texas) has long been a curiosity — a hard-to-figure iconoclast, even a bit nutty.

“Dr. No” is the guy who wants to abolish the Federal Reserve, refuses to vote for war funding when Congress hasn’t actually declared a war and drops oddball bills calling for the legalization of industrial hemp and interstate sales of unpasteurized milk. He’s a hard-core libertarian who doesn’t pull punches against his own party when he feels they’ve stepped over the line.

But Paul’s growing ability to raise money for his presidential bid — including an astounding $4 million in a single day last month — and his Internet-fueled celebrity have fellow Republicans taking notice and feeling at least a little bit uneasy.

For starters, Paul’s opposition to the Iraq War runs diametrically opposed to the party line, and he has exposed a fault line between the libertarian wing of the Republican Party and its leaders. Then there is the fear that Paul, who already has run for president under the Libertarian Party banner once, could be next year’s Ralph Nader-style spoiler for the GOP.

“My greater concern is that he runs as something other than a Republican in a third party next year,” said House Republican Conference Chairman Adam Putnam (Fla.), when asked whether he had fears about Paul’s message splitting the party.

Asked if Republicans need to be friendly to Paul to keep him in the fold, Putnam quipped, “We’re always friendly to him. He’s a great guy!”

Paul himself, who previously ran for the White House under the Libertarian Party banner, says he has “no plans” to run as an Independent or third-party candidate. But there is little doubt that a Paul third-party run could siphon off a few precious percentage points of disaffected libertarians who want to protest what they consider the nation-building excesses, foreign entanglements and massive debts of the Bush administration but don’t want to vote for a Democrat liable to tax and spend even more.

Rep. Pete Hoekstra (R-Mich.), who also has a strong libertarian streak, said he suspects Paul might be more tempted to bolt the party if Republicans had shut him out of debates and the primary process, but he has been given a fair shot. “He may toy with the idea. There is a concern of what he might do and that’s why the party has fully engaged him,” Hoekstra said.

Paul’s appeal has as much to do with his lack of equivocation as the ideas themselves, said Hoekstra, who is backing Mitt Romney and has urged him to outline bolder ideas.

“I think it does show you the frustration Americans have with the American political process,” Hoekstra said of Paul. “We don’t speak clearly.”

House Minority Whip Roy Blunt (R-Mo.) said despite Paul’s surge, he isn’t particularly relevant in the halls of the Capitol, and he isn’t too worried about the Paul phenomenon growing.

“He’s a principled guy … who votes a very narrow view of the federal government, even by conservative Republican standards that I think I reflect,” Blunt said. Paul’s overall view of government is “not a view that’s going to have a lot of impact on what we do here day to day. … That’s not to say that some of his ideas don’t have a lot of appeal or that Ron Paul personally doesn’t have a lot of appeal.”

Paul said he has received a surprisingly warm response on the House floor from his colleagues in both parties.

“I think they know I’ve always been sincere,” he said. “I think they respect me and they respect success. The reception has been much better [lately] than in the 30 years I’ve been in politics. It’s not that they endorse my views. I think they listen more carefully now.”

Democrats like his opposition to the Iraq War, though little else, while some Republicans see the surge for Paul — in intensity if not in broad support — as a symptom of wider frustration with politics as usual.

Paul still walks through the Capitol looking like a somewhat disheveled professor rather than an ascendant Internet rock star for the libertarian set.

Rep. Walter Jones Jr. (R-N.C.), a fellow war opponent who is backing Paul’s campaign and regularly sits with him on the House floor, said many more Members have been coming up to Paul now that he’s achieved a certain notoriety. “It’s been kind of interesting. They come up and kid him about raising money. It’s all in good humor. I think people are somewhat surprised that he’s doing well financially.”

One freshman Republican lawmaker even asked Paul for an autographed photo for her son, Jones said, while others tease him about a blimp being built with his name emblazoned on it.

There’s rarely any real lobbying, of course. It’s not hard to find out where the Texan stands.

“I think people know that Ron Paul is Ron Paul,” Jones said. “He’s a unique icon, really.”

GOP leaders generally ignore him now that he no longer is needed for close votes (not that they could count on him when they were in the majority anyway). Paul himself said the pressure is off because “now that the Democrats are in charge, leadership is opposed to spending.”

Paul, meanwhile, continues to put in numerous bills, and even constitutional amendments like getting rid of birthright citizenship, although none of them is likely to ever see the light of day on the House floor, let alone a Congressional hearing. Paul has proposed numerous massive tax cuts, rather than the more tepid tax cut extensions of Republicans generally.

Occasionally he finds common ground with liberal Democrats. His industrial hemp bill has backing from some of the most liberal Members of Congress, including Education and Labor Chairman George Miller (Calif.), Financial Services Chairman Barney Frank (Mass.) and Rep. Lynn Woolsey (Calif.). Paul also wants to get the United States out of the United Nations, give citizens the right to bear firearms in national parks and ditch gun-free school zones.

Usually he has at least a few co-sponsors, but some are pure solo acts. He’s the only Member willing to call for abolishing the Federal Reserve system outright. (Paul trusts gold more than he trusts Alan Greenspan.)

Paul has proposed eliminating withholding taxes and supports forcing individuals to pay their taxes in monthly installments “to restore to taxpayers the awareness of the true cost of government.” Waiters and waitresses would not have tips taxed. Doctors could deduct their malpractice insurance — something the old doctor knows a thing or two about.

He even wants to get rid of duties on lutetium oxide, a metal used in making lasers and in other industrial applications, as well as on phosphoric acid, lanthanum salt and “cerium terbium-doped.”

He also wants to prohibit production of the penny unless and until it can be determined whether there is a surplus of said pennies already in circulation.

Rep. Jeff Flake (R-Ariz.) attributes the intensity of Paul’s backers to a deeper-seated frustration with the Republican Party. “No doubt the party has had a hard time and I think it’s largely because we haven’t lived up to our propaganda about limited government,” Flake said, pointing to Republican leaders’ refusal to oppose earmarks.

Jones said he hopes a strong showing in New Hampshire, where independents can vote in the Republican primary, will catapult Paul into the first tier of candidates.

“If he should run third or fourth in New Hampshire, that puts him in a different category,” Jones said, and makes him harder for the media and his fellow Republicans to dismiss. “A kook doesn’t get that kind of support.”

Jones said he doesn’t think Paul will bolt the party but figured he might be more tempted if he was younger. Paul is 72.

“There is a lot of frustration out here because Republicans are not supposed to be expanding the federal government,” Jones said. “This country is looking for a third party. The country is in trouble.”