Libertarians — people who cringe at intrusive government, high taxes, nation-building and politicians telling them how to behave — could turn out to be the key swing voters in Tuesday's contentious midterm election.

And, in an unusual development, that might not bode well for Republicans this time around.

A number of political scientists and libertarian pundits say that libertarian voters who sided with the Republicans in the past have become disgusted with bloated federal spending, the war in Iraq and prevailing social conservatism in the GOP-dominated White House and Congress. Many feel libertarian voters will either vote for Democrats on Tuesday or just stay home, and that could play a role in deciding key battleground races.

• Click here to visit YOU DECIDE 2006, FOXNews.com's complete election center.

Check Your State, Check Your Race by clicking BALANCE OF POWER dropdown menu above.

"Republicans need to be taught a lesson — that they can't keep thumbing their noses at us," said Chuck Muth, president of Citizen Outreach, a libertarian think tank in Washington.

“Very few of us will vote Democrat. A lot of us will stay home,” he said.

Muth, who lives and works in Nevada, has long considered himself a Republican. But not this year. He points out that libertarians aren’t necessarily card-carrying members of the Libertarian Party, but have long toiled away in the conservative movement of the Republican Party.

"A lot of columnists and conservative leaders in the movement are saying, I don’t care how angry you are, you have to go out and vote Republican," Muth said. "No I don't. They haven't earned it."

For months, the cracks have been showing in Republican support from the usual backers: in the most recent FOX News Poll, 78 percent of Republicans said they were definitely voting Republican on Tuesday, a drop from previous election cycles.

PDF: Click here for complete poll results.

“We are seeing greater solidarity among Democrats than among Republicans,” said Scott Keeter of the Pew Center for the People and the Press, which has conducted extensive public opinion polling throughout the election cycle.

While Republicans have recently been courting wary social and religious conservatives with a media blitz that concentrates on border protection and gay marriage, those who consider themselves libertarian-conservatives say they feel they have been given the shaft for the last six years.

"With libertarians you have to worry about turnout and whether they might even vote Democrat," said David Boaz, vice president of the Cato Institute, which in October released "The Libertarian Vote" with David Kirby, executive director of the America's Future Foundation.

The Cato report, which crunches numbers from the Pew Center, the Gallup Governance Study and the American National Election Studies, asserts that voters with libertarian ideals make up about 13 percent of the electorate, and though they preferred George W. Bush in the last two presidential elections, the president's support actually declined among these voters from a 50 point lead over Al Gore in 2000 to a 21 point lead over John Kerry in 2004.

“That was the original reason why I got into this race,” said Brian Houillion, a Libertarian Party candidate for Congress in the conservative 4th District of Kentucky, where former Democratic Rep. Ken Lucas is running neck-and-neck with GOP Rep. Geoff Davis.

“In our area, in northern Kentucky, I saw how voters have become disillusioned and disappointed with our system,” he said. “I saw Republicans, who through the 1980s and '90s were trying to be fiscally conservative and trying to limit government and its power, not doing that anymore. They’re trying to make government bigger than even the Democrats before them.”

According to Pew, libertarians make up around 9 percent of the electorate. They also find that 50 percent of libertarians typically identify with or lean Republican, while 41 percent identify or lean Democratic and 9 percent are independent or unaffiliated.

About 18 percent of independents in today’s electorate hold libertarian values, according to Boaz, suggesting that if libertarians are indeed looking for a change, they could be playing a role in the strong independent movement toward Democrats this year.

According to an October Washington Post/ABC News poll, independent voters are supporting Democrats 2 to 1 over Republicans.

“I think if libertarians don’t have someone from the (Libertarian Party) on their ballot … I think a strong number of them will vote for the Democrats,” said Butch Morgan, a Democratic Party official in the 2nd Congressional District in northern Indiana, where Democrat Joe Donnelly is giving GOP incumbent Rep. Chris Chocola a run for his money.

Disaffected Republican voters who say GOP-led Washington has led to bloat and bad government are the ones who can really affect the turnout on Tuesday, he said.

“I’m hearing a lot of that at headquarters,” said Morgan. “A little balance is what they are looking for. That is what people are telling us and we’re listening to them.”

But not everyone is convinced that Republicans — even those with libertarian values — are leaving the party in droves. Carol Tabor, president of Family Security Matters, said national security is still a top issue among Republican voters, and they are not likely to vote for a Democrat on that score.

“It depends on turnout — I wish I had a crystal ball,” she said. “While there is a tremendous disappointment in the Republicans, its not enough to punish them by not voting for them,” particularly when they feel Democrats are so bad on the issue.

Ed Patru, spokesman for the National Republican Congressional Committee, said libertarians certainly aren’t going to find solace with the Democrats, who he says have made it “crystal clear in unambiguous terms that they want to repeal the tax cuts and tax relief as we know it.

“Along with that, they’ve promised billions of dollars in new spending … and bloat the size of government beyond what anybody can imagine,” Patru said.

But Keeter points out that national security isn’t as hot an issue among voters as it was in 2002 and 2004 and concern about the Iraq war has consistently topped their surveys among voters.

“A lot of what happened in 2002 and 2004 was some of these (swing) groups’ ideological views were overshadowed by national security and the War on Terror. We know that terrorism is not as prominent an issue for people today,” Keeter said.

“I think if libertarians are not making up their mind on the basis of terrorism they are open to persuasion by Democrats today because of issues like gay marriage, stem cell research,” he said, noting that libertarians do not think the government has any place in deciding who can marry, and should not impede on important medical research based on moral beliefs. "You can see libertarians taking more things into account as they make their minds up.”

• Click here to visit YOU DECIDE 2006, FOXNews.com's complete election center.