The issue continues to be that if you want to play ball in American politics you have to subvert one of the two bought out parties, any outside party push has historically been dead before it started.
I've heard this all my life, yet I have never seen a serious attempt at a third party. To counter this claim there have been numerous third party presidential candidates that have broken the 10% margin. Teddy Roosevelt got the second highest amount of votes running for his Bull Moose Party in 1912, (27.4% to be exact).