Why hasn’t a third political party caught on?

In Great Britain this week, a center-left political party ? the Liberal Democrats ? played the power broker in recent elections, teaming up with new PM David Cameron’s Conservative Party to create the first coalition government in Britain in 70 years. Could a third party ever play kingmaker here, in the United States?

A new NBC/WSJ poll suggests that many people wouldn’t object: More than 80 percent see problems with America’s two-party system, and nearly one third of the country believes that America needs a third party.

Micah Sifry, author of “Spoiling for a Fight: Third-Party Politics in America,” and editor of the Personal Democracy Forum, looks at why third parties have mostly failed in the American political landscape, whether that’s likely to change, and if there’s a single type of third party on which Americans could ever agree.