First, I will say that I'm not one of those people who thinks that the two-party system is superior and must be maintained. People who argue that are usually a) idiots, or b) party hacks.
Here's the problem: every third party startup wants to field a candidate for every position in America, from President to dog catcher. Supposedly, this will raise awareness of their party and make them look like a viable alternative. Unfortunately, this will never work, because money is wasted in campaigns that these parties can never win.
I think the Libertarians are doing it right. They have targeted New Hampshire as their "Free State Project." So a whole bunch of them are moving to NH over the next four years (I think) so that they will have a sizable population there. They are then going to build a grassroots party movement and start gaining local offices. If their plan works right, NH residents will get to see the results of Libertarian-dominated government, like what they see, and vote in more Libertarians. Eventually, they will be a major party in NH, and that is supposed to spark a Libertarian fire nationwide.
This plan, IMO, has a better chance than an unknown party running a Presidential candidate with no chance of winning, just to get their name on the ballot.