"You need to take a longer term view. Your vote serves to do more than simply help that candidate win that election. It also serves to increase (however slightly) the profile of that candidate, and by extension the party. Every vote that goes to a third party is one that helps further the belief that a third party candidate is viable." - CecilPL
I've read hints about this idea recently and this really exactly says what I thought the hints were getting at. I think one 4-year election cycle would be enough for a third political party to become viable.
It seems to me that those who want a third party have been viewing their votes as wasted on third party candidates and voted for whomever of the two dominant parties is perceived to be the lesser of two evils.
If those same people voted for third party candidates, not just as a vote for the candidate but as a vote for the party, I think one election cycle would be enough to bring the party to a position where it has to be reckoned with. The next cycle may not have a lot of winners in the third party but it would continue to grow as long as it offered a platform that was substantially different from the other parties' platforms. Of course, once they have to reckoned with then the other parties' will have to look at how to keep loyal members from defecting to the real change and so all of the politics could change.
I just love how well this writer stated it.
(I'm no expert, I just wanted to write this while it was on my mind.)