There will be a third party that is successful in America, but only after the ineffectiveness of Congress goes to unhealthy new depths that show the American voters that the GOP and Democrats won't get anything done. Libertarians probably have the best chance of making any headway in American politics in terms of a viable third party. Ron Paul is the closest thing to a Libertarian that Congress has had for a long time.
It is possible that a third party may become influential in America. People are becoming more and more dissatisfied with both parties of the government. All it will take is for enough people to become upset. Also, a good third party needs to arise. One that is well funded, then this party will become influential.
I believe that Americans are growing increasingly tired of our current two party political system in this country. We have seen in the recent past a third party grow to the media's attention. This party of course was the Tea party. In addition to the Tea party there have been two other major third parties such as the Libertarian party and Green party. The libertarian party has increased in popularity over the past few years mainly due to its fusion of many conservative and liberal views.
I don't think that there will ever be a truly influential and relevant third party in the United States. We are now culturally hardwired to accept two major national political parties as the norm. Third parties are seen as just a quaint and amusing side show for college students still figuring out life. The Tea Party crazies understood this, which is why they took over the Republicans instead of going it alone.
Third parties will never be successful in the American political system. The closest it came was Ross Perot in 1992 and he only got less than twenty percent of the vote. He did keep George Bush from being President and Bill Clinton won the election. The two party system will live on forever.