"They're looking for a change and a shift," Mr. Cory said. "They're sick of same old politics as usual and are looking for a viable alternative, and we're that viable alternative."
Libertarians are known as advocating a free market, nonintervention in foreign policy, and small government that is fiscally conservative and socially liberal. About 250,000 Americans are registered with the Libertarian Party, officials say.
"Several things set us apart," Mr. Cory said. "People try to pigeonhole us into being opposed to the war on drugs, which we are, but we're the only party out there advocating our promise of smaller taxes, smaller government and more freedom."
Mr. Cory said the Libertarian Party's numbers began increasing in January, when Democrats took control of Congress.
"We were actually a bit worried about that, whenever Dems took control, simply because we thought the left will be placated by this and they'll think their people will be in power and make everything right," Mr. Cory said. "But I think [House Speaker] Nancy Pelosi and others have shown they don't have the backbone to bring the troops home."
Democratic Party officials did not respond to requests for comment. Tracey Schmitt, press secretary for the Republican National Committee, said "despite the difficult political environment, people continue to be attracted to the fundamental ideals of the Republican Party."