A 3rd party is not possible in America. Blacks vote Democrat at a rate of 90%. Hispanics vote for Democrats at 70%. It has been like this for well over 60 years.
A third party would split the white vote to such a degree that it would be impossible for the Democratic party to ever lose. As it is because of this strong allegiance to the Democratic party the Republicans can only really hold presidential power by winning the electoral college. Unless these allegiances change there will never be a relevant 3rd party in America..