[BluffTHIS!]

Anyone who sincerely wants to see a 3rd party become a force in US politics has to be willing to vote that way over and over no matter what the consequences. That means you vote for Nader-like candidates time and again even when it is likely you are insuring the win of the major party candidate you would least like to see in office. It is the fear of getting the least preferred choice, along with the major parties slowly synthesizing 3rd party ideals on both sides of the political spectrum, that keeps 3rd parties permanently on the sidelines.

The only alternative is an agenda type of coalition, in which right leaning dems and left leaning repubs back a centrist agenda and urge citizens to vote for the candidate of whatever pary that backs that agenda. Of course those politicians have to also be willing to buck party discipline of their respective parties and accept the consequences that come from that.