I doubt any 3rd party will go far, but they do help. When the green or libertarian party starts to gain votes, the democrat or republican party changes their po

I doubt any 3rd party will go far, but they do help. When the green or libertarian party starts to gain votes, the democrat or republican party changes their policy to include concepts that the respective party had. So in the end, one of the 2 main parties will win. But their ideologies will be changed due to the third party.