A history of third party candidates...

[Virginia Dare]

Doing a little research, I found this interesting...

The American system is commonly called a "two-party system" because there have historically been only two major political parties with candidates competing for offices (especially in federal elections). The first two political parties had their origins in the debate over the ratification of the Constitution--the Federalists and Antifederalists. Today, the Republican and Democratic Parties dominate electoral politics. Almost every federal or state-level elected official in the United States is either a Republican or Democrat. In fact, in the United States Congress, there is only one member in the House of Representatives that is not a Republican or a Democrat--Rep. Bernie Sanders of Vermont is an Independent. Every other House member and Senator belongs to either the Democratic or Republican Party.

The American two-party system is the result of the way elections are structured in the United States. Representatives in the Congress and in state legislatures are elected to in single-member districts where the individual with the most votes wins. Because only one party's candidate can win in each district, there is a strong incentive for political competitors to organize themselves into two competing "teams" or parties. By doing so, party members and their candidates maximize their chances of winning elections. (In some countries where there are multi-member districts, parties that win smaller percentages of the vote can often win legislative representation. Consequently, in such systems, there is an incentive to form smaller "third" parties.) Other features of the American system of elections, such as campaign finance rules, the electoral college and rules giving party candidates ballot access further solidify the two-party system in the United States.

The same features of the American system that have encouraged a two-party system also serve to discourage the emergence of third parties. When third parties have emerged in American political history, their successes have been short-lived. In most cases, the issues or ideas championed by third parties have been "stolen" by the candidates of one of the two major parties. Sometimes the issue position taken by the third party is even incorporated into the platform of one of the existing parties. By doing so, the existing party generally wins the support of the voters that had been the support base of the third party. With no unique issues to stand on and depleted voter support, third parties generally fade away.

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further down the article there is a chart showing the historical third party candidates and how they did...

http://www.thisnation.com/question/042.html