We already have 5 on a de facto basis.We need more parties. Start with extreme Left and extreme Right and get at least 3 others in between.
The extreme left is Bernie's Bolsheviks.
The moderate left is Nancy Pelosi and Hillary Clinton.
The centrists are the nonpartisan/independents -- neither DEM nor GOP.
The moderate right is the GOP -- mostly -- the ones called RINO.
The far right is the T-Party and fruit baskets like Cruz, Rand Paul, etc.