The two party system is the result of our winner take all approach to representative government. You'll find that third, fourth, etc. parties only exist in systems using what is known as proportional representation. PR for short, sets rules where representation in the legislative body is established by what proportion of the total votes cast were won by a given party. If, for instance, the Pea Green Envy party receives 24% of the total votes cast in an election, then they will have 24% of the seats in the Legislature.
In virtually all governments where representatives are selected "first past the post" FPTP, the system evolves into two parties. Great examples are, of course, the US, and the Westminster parliamentary system of Great Britain.
Two parties are an inevitability with FPTP. The only way to legitimize a third party is to totally change how we elect our representatives, which would mean re-writing virtually all electoral law in the US.
We have what we have, and it is a good system that has produced the most powerful Nation the World has ever seen; but, we definitely need to know how to "work" the system to our advantage.
Regarding Ron Paul, I did vote for him in the Primary for President, but of course, Romney had dropped out, so we were left with Skelator, I mean McCain