Sure, there’s the Nader factor in the presidential election.

But what about the Bailey factor in North Carolina?

That would be Tom Bailey, the Libertarian candidate for Senate in the Tar Heel State.

With perhaps a dozen close Senate races on tap next week and a slightly greater number of competitive House races, there are several where independent and third-party candidates could make a difference, even if they capture a mere 1 percent of the vote.

Think third-party candidates don’t influence the outcome of Congressional elections? Just ask Sen. John Ensign (R-Nev.), former Sen. Slade Gorton (R-Wash.) and ex-Rep. John Thune (R-S.D.).

Richard Winger, editor of Ballot Access News and an authority on third-party politics, said that in each of the past three cycles, the Libertarian Party cost Republicans a Senate seat: in Nevada in 1998, when Ensign lost to Sen. Harry Reid (D) by a mere 428 votes; in Washington in 2000, when Gorton was knocked off by Maria Cantwell (D) by 2,229 votes; and in South Dakota in 2002, where Thune lost to Sen. Tim Johnson (D) by just 524 votes.

The irony behind Thune’s defeat is that the Libertarian candidate, Kurt Evans, dropped out of the contest a few weeks before Election Day and endorsed Thune. But his name remained on the ballot, and he took more than 1,000 votes.

It may be some comfort to Thune and Republicans that, as he makes a second run at the Senate against Minority Leader Tom Daschle (D), no third candidate is on the ballot.

“Every one of the most competitive Senate races except South Dakota has” third party candidates this year, Winger said.

But not all third-party candidates are created equal — and their cut of the vote affects Democrats and Republicans in different ways.

In Alaska, for example, Green Party nominee Jim Sykes was expected to be a major factor in the super-tight Senate contest, siphoning critical liberal votes from former Gov. Tony Knowles (D) in his challenge to Sen. Lisa Murkowski (R). Sykes received 7 percent of the vote in the far less competitive 2002 Senate race, and early polls this time showed him getting at least 4 percent.

But while he could still be a factor next Tuesday, Sykes’ percentage of the vote has shrunk in more recent polls. In mid-October, he was polling at just 1 percent, while Knowles held a lead of 1 point to 3 points. Meanwhile, the Alaska Independent Party and the Libertarian Party were also fielding candidates, creating the potential to pull conservative votes from Murkowski.

Another third-party Senate candidate expected to get a decent share of the vote is Jim Clymer, the nominee of the Constitution Party in Pennsylvania. In a race where both major party nominees — Sen. Arlen Specter (R) and Rep. Joe Hoeffel (D) — support abortion rights, Clymer is the most prominent anti-abortion candidate on the Senate ballot.

While Democrats are pinning their long-shot hopes on Clymer hurting Specter — he has scored as high as 7 percent in some polls — Hoeffel continues to trail Specter by a considerably wider margin, diminishing the possibility that Clymer will wind up being a spoiler for the Republicans.

In Oklahoma, eccentric Independent Senate candidate Sheila Bilyeu has done surprisingly well in some recent polls, pulling 6 percent in one survey released last week. That could hurt Rep. Brad Carson (D) in his dog-fight with ex-Rep. Tom Coburn (R).

Bilyeu doesn’t even live in the Sooner State — “No voter will know anything about her,” Winger said, so her surprising showing may be a reflection of voters’ disgust with the intensely nasty campaign Carson and Coburn are waging against each other. On the other hand, Oklahomans gave 14 percent of the vote to an Independent candidate for governor in 2002, though he was a wealthy businessman who was reasonably well known.

And what about Bailey, the Libertarian Senate candidate in North Carolina? A Libertarian won 1.5 percent of the vote in the state’s 2002 Senate contest, and 1.8 percent of the vote in the 1998 election for the seat that’s up now. Polls continue to show Rep. Richard Burr (R) and former White House Chief of Staff Erskine Bowles (D) neck and neck in the open-seat race.

But Brad Woodhouse, a spokesman for the Democratic Senatorial Campaign Committee and a veteran North Carolina political operative, said winners of close races in the Tar Heel State tend to prevail with perhaps 52 percent of the vote — meaning Bailey isn’t likely to be a decisive factor.

“The race I don’t think is going to come down to 1 or 2 points,” Woodhouse predicted. “Somebody gets a little wave at the end.”

Doug Heye, a spokesman for Burr’s campaign, said the Republican camp did not want to comment on Bailey.

“We’re focused on Erskine Bowles,” he said.

Meanwhile, third parties could be a factor in some close House elections — most intriguingly in the five Texas races where Democratic incumbents are fighting for their political lives in new district lines pushed through by Republicans last year. All five districts have Libertarian candidates, and in the 32nd district slugfest between Reps. Pete Sessions (R) and Martin Frost (D), Michael Needleman could make a difference.

“They vote for Libertarians in Texas,” said Greg Speed, a spokesman for the Democratic Congressional Campaign Committee.

Other close House races where third-party candidates pose a potential threat to Republicans include the open-seat race in Washington’s 8th district, where Libertarian nominee Spencer Garrett vows to “take away pain caused by computers, networks and bloated government”; Kentucky’s 3rd district, where Libertarian George Dick could take conservative votes away from Rep. Anne Northup (R); and South Dakota, where Libertarian nominee Terry Begay took 1 percent of the vote in 2002.

A potential problem for Democrats lurks in Kentucky’s conservative 4th district, where the party is trying to hold on to the seat being vacated by Rep. Ken Lucas (D). There, Independent Michael Slider, a teacher and Ralph Nader supporter, is waging a populist “throw the bums out” campaign that could draw votes from the Democratic nominee, Nick Clooney.

In Utah’s 2nd district, Rep. Jim Matheson (D) may have to worry about Green Party nominee Patrick Diehl, who took 1.2 percent of the vote in 2002. But Republican John Swallow may lose votes to Jeremy Petersen, the Constitution Party nominee, and Ronald Amos, running on the banner of the Personal Choice Party.

If any of these House candidates wind up being spoilers, it will almost be by accident, Winger predicted.

“There’s no [third party] U.S. House candidate that I’m aware of that has a lot of money and is trying really hard,” he said.