Republican candidates are pulling out all the stops to bring disgruntled conservative voters home on election day. Dozens of conservative talk show hosts were invited to the White House to interview Vice President Cheney, political adviser Karl Rove, and other top officials.

President Bush and his colleagues are telling voters that no matter how unhappy they are with Republicans, they’ll like Democrats even less.

But evidence from around the country suggests that even if the conservatives come home to the Republican Party, the GOP could still lose Congress by losing libertarian voters.

Take a look at independent voters. There are more of them than before, especially in the West. More than 25 percent of Arizona voters now register as independent or third-party voters. And according to a Washington Post-ABC News poll, they’ve shifted sharply toward the Democrats in this fall’s elections.

But independents haven’t fallen in love with the Democrats. They seem to be motivated more by dissatisfaction with Republicans than enthusiasm for Democrats. A New York Times-CBS News poll found that 58 percent of independents would prefer that candidates run without party labels at all. In that regard they reflect the views of the entire electorate. A recent Gallup Poll found that by 48 to 45 percent, Americans would like to see a new major party, up from 56 to 40 against a new party in 2003.

Meanwhile, Republicans are slipping in places like the Mountain West where they should do well even in a Democratic year. The national Republican Party is spending big money to save Republican seats in western Idaho, eastern Washington, Colorado Springs, southern and eastern Arizona, and Wyoming. Why would rock-ribbed Barry Goldwater individualists from Idaho to Arizona consider voting for Democrats?

The secret word that ties all these Republican problems together is “libertarian.” Pollsters and politicians tell us that everyone is liberal or conservative, blue or red, Democrat or Republican. But new research shows that about 15 percent of American voters hold libertarian views. They’re small-government, leave-me-alone voters who don’t like big-spending Democrats or religious-right Republicans.

Libertarians usually vote for Republicans, who promise to hold down taxes, spending, and regulation. But in the past six years of Republican control in Washington, federal spending has skyrocketed. Meanwhile, the Republican Party has become more dominated by the religious right, and the Bush administration has mired the country in a seemingly endless war in Iraq.

Libertarians see less and less reason to vote Republican. In 2004 many of them switched. President Bush won 72 percent of the libertarian vote in 2000 but only 59 percent in 2004. John Kerry almost doubled Al Gore’s share of the libertarian vote, from 20 to 38 percent. That was a net swing away from Bush of almost 5 million libertarian votes. If he had held those votes, he would have had an easy reelection. Instead, he squeaked out another narrow win in the electoral college.

Political observers often note that a switch of only 60,000 votes in Ohio would have given the election to Kerry. But as Ryan Sager notes in his book The Elephant in the Room, a switch of 70,000 votes in Colorado, New Mexico, and Nevada would also have given Kerry the victory.

Now the unhappy libertarian voters are threatening Republican congressional seats in the Mountain West. Republicans will warn about the high taxes voters can expect from a Democratic Congress, and that will keep some libertarian voters in the GOP camp. But war, corruption, overspending, and an excess of social conservatism will cause many others to stay home or vote Democratic.

Both Republicans and Democrats are just starting to wake up to the libertarian vote, but it will get more attention in post-election analysis and in both parties’ plans for 2008.