Perhaps IF the feds were to hand out more cash to everybody except the two major parties, there would be such a possibility, now wouldn't you agree?
Once upon a time, they were handing out money to the Reform Party...and then Buchanan cratered it.
Hell, the Libertarians could qualify for federal matching funds (a sign of seriousness; an even greater sign of said seriousness would follow when they turned down those funds on principle) at 5% nationwide, IIRC.
Bottom line: they'd rather be a bunch of a$$clowns than do anything that might actually get them closer to winning an election.