Why do minor political parties have such little success competing in U.S. elections? Short of winning elections, how do third parties have influence on the political system?Would you ever consider voting for an independent or a third party candidate? Why or why not?

Why do minor political parties have such little success competing in U.S. elections?  Short of winning elections, how do third parties have influence on the political system?Would you ever consider voting for an independent or a third party candidate? Why or why not?