The United States has become stagnant when it comes to political parties and their ideas. In reality the two parties, in general, are not even that different from each other. People have become frustrated by the major parties, especially since 2000. The interesting thing is that despite these struggles none of the other parties in the country have been able to make any headway on the national scene.
The lack of a third party is a system by design. Throughout history there have been two parties with very few exceptions (and these exceptions were largely a party replacing another). In the modern era the two parties we know today have done their very best to prevent a third party from rising up (the Democrats and Republicans work very well together when it comes to making sure they stay in charge). From funding laws, to the primary system it is close to impossible for off party candidates to get elected (See my recent post on Campaign Finance Reform for some of the details on that issue).
With all the strife it would seem logical that now would be a good time for another party to make a splash. While it sounds like a good idea I really do not think it would work, nor would it make any difference. What it boils down to is this: The Presidency is not enough. A third party president would, in the current federal system, essentially become a figure head at best. With no allies in the house or senate a third party president would be forced to just go along for the ride, or alternatively veto a lot of bills and get nothing done.
The current two parties in power would have to pass legislation that would make it easier for third parties to become a strong contender; this is never going to happen for much the same reason that there will never be term limits for congress, nobody is going to make laws to fire themselves, its just not logical. Therefore in order for a third party to become a viable entity it would take a miracle of widespread winning, most likely during a presidential election year. A full sweep of the available 1/3 of the House seats open...and at least 20 senate seats in one go round to establish a foothold strong enough to continue to hold power and also have the votes to make an impact.
The 3 largest "third-parties" in the United States are: Green, Constitution and Libertarian. None of these have had any true success in running a candidate. The Reform party had some success in the past, earning enough votes to qualify for funding, however due to the reckless actions of Pat Buchannon and the in-fighting in the party they have dwindled to insignificance. The Libertarian party has the largest number of registered members outside of the two major parties, so logic would state that they would be the best chance, but their most likely a bit to radical to win large numbers of elections. This brings me to the next point.
Most Americans are very centrist. There may be arguments over abortion or immigration but when it comes down to the majority of issues we are largely moderate. So are the majority of rank and file members of Congress. Even the most zealous politicians from the far sides of either direction tend to drift towards the middle over time. You simply cannot get anything done if you are too radical. While it is unfortunate that people do not necessarily feel that there is a candidate that aligns with their views perfectly, the addition of a third party simply would not change that. Human beings are all different. Nobody is going to agree/align with you 100% of the time. This has led to our candidates pounding on a few key issues. Lately its been health care, abortion and gay marriage. These are issues that people have opinions on. They tend to be strong opinions and this is why candidates use them. They look at polling data and then jump on the side of plurality and drive it home (i.e. Liberals tend to be pro-choice...democrats run campaigns based on this. Conservatives tend to be very zealous when it comes to immigration reform...Republicans campaign to build a wall) The point being that campaigns are based on the majority and such there is no where to go, in my case I am strongly pro-choice, but I despise unions...well do I vote for the pro union, pro choice democrat or the pro life anti union republican...
To avoid rambling further, I shall conclude. A third party will never succeed in this country in my opinion. People vote on limited issues that they have strong opinions on. They are divisive issues with no center point of view for the most part. A third party simply doesn't have enough ground to stand on to make a case that they would be better. If a third party did arise, it would have to be floating in its ideology, following the opinions of independent, likely voters...it would be the party of ever-changing positions. They could call it the FlipFlop party because essentially that is all they could do. The only way to truly end the two party system would be an Amendment to switch our Congressional elections to a plurality representation system and to do away with the Electoral College.