Ron Paul could be the Ralph Nader of 2008. Only this time, a third-party candidacy could hurt the Republicans, not the Democrats.

For now, Mr. Paul’s campaign is dismissing talk of a run as anything other than a Republican, and the candidate himself is focused on the primaries. “Ron’s committed to running for the Republican nomination or nothing,” a spokesman for Mr. Paul, Jesse Benton, said. Mr. Paul, who ran as a Libertarian presidential candidate in 1988, said the same to the Wall Street Journal last month. Nevertheless, the relative success the Texas congressman is having on the campaign trail has political observers envisioning how a Paul third-party candidacy would shake out.

The possibility of a candidacy by Mr. Paul on the Libertarian ticket began being discussed in earnest after last month’s Republican debate in Michigan, when Chris Matthews of MSNBC asked him if he promised to back the Republican nominee. “Not right now I don’t,” he said, adding, “Not unless they’re willing to end the war and bring our troops home, not unless they’re willing to look at excessive spending.” In an election that pitted, say, Mayor Giuliani against Senator Clinton, at whom the anti-war movement has bristled, Mr. Paul might find a rationale for a candidacy. And given Mr. Paul’s strong fund-raising numbers during the third quarter of 2007, his campaign having garnered $5.2 million and possessing $5.4 million of cash on hand, he has outperformed expectations.

“Would he hurt the Republicans? The answer is yes. Could he hurt them somewhat in the Deep South?” a Democratic strategist, Hank Sheinkopf, said. “Could he do to them what Ralph Nader did to the Democrats in 2000? The answer is yes.”

Mr. Paul’s presence is currently making itself felt on the Internet, where he is raising almost 80% of his money, and on the ground in New Hampshire, where his sign-holding supporters are a frequent sight on the campaign trail. In New Hampshire, Mr. Paul’s campaign has distributed a direct mail piece and produced radio and television ads giving informed Republicans the sense that he may finish as high as third place in the Granite State, which Patrick Buchanan won in 1996 with a somewhat similar, though not identical, angry outsider message.

A former political consultant to Jesse Ventura and Ralph Nader, Bill Hillsman, the president of North Woods Advertising, said a third-party candidacy for Mr. Paul could pick up steam. “You can see the potential there for something if he had some breakthrough messaging,” Mr. Hillsman said. “He’s got a little bit of money and some strong supporters. It reminds me of the Jesse Ventura thing in Minnesota. His people sound pretty dedicated. You can go a long way with that kind of dedication and support.” Asked whether there was a possibility Mr. Paul could draw from the right and left, Mr. Hillsman said “I think there could be. … If they don’t like their choices in a general, it could happen.”

Mr. Hillsman, however, recited several obstacles to Mr. Paul if he decided to run as a third-party candidate, including ballot access and fund raising. “I don’t think he’d get to Perot-type numbers,” he said.

A founder of New York’s Independence Party, Laureen Oliver, said that while a Libertarian label might help Mr. Paul get on the ballot, it would also cap his appeal by so strongly identifying him with a party that has not won many votes in the past. “The same thing that can get him on the ballot is the same thing that can hurt him,” said Ms. Oliver, who, along with Mr. Hillsman, has founded a political consulting firm aimed at independent and third party candidates.

A race between Mr. Giuliani and Mrs. Clinton might be the most likely to create a rationale for a Paul candidacy. “If you have Giuliani versus Hillary, you have two big government candidates. You have two candidates who are pro-interventionist and hawkish,” said the executive vice president of the Libertarian-leaning Cato Institute, David Boaz. Mr. Boaz added that such an election, with each candidate’s supporters demonizing the other candidate, might make some room for a different kind of candidate, such as Mr. Paul. “The question is, are there people in America who don’t line up with this red-blue approach? I think there are,” he said.

Still, Mr. Boaz said he credited Mr. Paul’s assertion that he was not interested in running on a Libertarian line this time. Unlike the primary fight, during which Mr. Paul has been able to raise his profile with debate appearances, Mr. Boaz said he would likely not be allowed into general election debates. “He’s gotten more coverage as a Republican than any Libertarian candidate has ever gotten,” he said.

The distinguished fellow in conservative thought at the Heritage Foundation, Lee Edwards, said that while Mr. Paul might be “appealing to some of the paleo-vote that went for Pat Buchanan in 1996,” he didn’t see Mr. Paul drawing much support from anti-war voters as a third-party candidate. “I don’t think there is a lot of isolationism,” Mr. Edwards said. The anti-war vote, he said, “is going for [Barack] Obama. I don’t see them going all the way over and backing a Libertarian candidate.”

One theory, being put forward by Jay Severin, a former consultant to Mr. Buchanan’s 1996 campaign and talk show host on Boston’s WTKK, is that Hillary-hatred will trump dislike of Mr. Giuliani or other Republicans among those generally-conservative minded. “If Hillary is the opponent, it’s going to suck all the wind out of the sails that might induce people to be frustrated and want to vote for somebody other than the Republican,”Jay Severin said. “He’d be like a Ralph Nader, only he’d get fewer votes.”

Ronald Radosh, a contributing editor of The New York Sun, said he could see a foreign policy-based rationale for a Paul campaign. “Foreign policy will trump all,” he said. “The MoveOn Democrats would be dissatisfied with Hillary and a lot of the paleocons who are against interventionism would look to him.”