It's never even really come close in Canada where we have 4 significant political parties but only 1 of 2 (Liberals or Conservatives) has ever won. It's marginally better here because we get to vote for Tweedledee, Tweedledum and Tweedledummer.
Of course being a Canadian living oustide of the province of Quebec I don't even get a chance to vote for the 4th party's leader; Le Tweedledum. BTW we get to vote for the 3rd time in the past 5 years on October 4th, due to the inability of our system to guarantee a clear winner.
The lengthy build up to the selection of presidential candidates and the final election in the US, IMHO appears to be all about money and marketing. With marketing and momentum being so critical I can't see how any 3rd party could really have a chance. A complete collapse of the US economy too an extent greater than the great depression would probably have to occur.