This won't fly.
The USC is silent on political parties -- as long as the same rules apply to everyone, they can have any rules they want.
I'm afraid it already has flown. the lesson of the 2000 election "aftermath" in florida is that where the law is silent, mischievous lawyers are more than capable of creating chaos, especially when they are assisted by activist state judges.
and the phrase "disenfranchising minority voters" was used intentionally to open up nearly countless areas of potentially valid legal arguments.
I posted an article by ted olsen yesterday that spoke to the possibility of this whole thing winding up in court.