That will never happen due to "winner takes all" laws in the States. For example, if you have 5 electors, and manage to get 2 of them third party, all it takes is for the other 3 to agree on a candidate for that guy to win all 5.
In states like Florida and Ohio that have a large number of electors, the winner takes all laws is what keeps the two parties in power.
The only way to cure it is to do away with the electoral college and go solely with the popular vote. I believe the reasons for the existence of the college, namely the problems of large distances to travel and no mass communication systems, have been solved.