The one that hasn't formed yet because the electorate has failed to recognize that parties only exist because they can consolidate mass political power. This is part of the "apathy" category. People don't care enough to meet up on this issue. They don't even care enough to be members of the existing parties or do more than show up to elections (and then, only between half and three-quarters for President, less for Congress, and hovering around 10-20% for primaries).
People care, but not enough to overcome institutional inertia.
> The one that hasn't formed yet because the electorate has failed to recognize that parties only exist because they can consolidate mass political power.
This is not the reason. The reason is the how the system was designed:
The Tea Party Republicans are a counter-example (or more accurately, a counterinsurgency). While there are still only two parties, one of them has become something that would be nearly unrecognizable to its members from the '70s.
It is possible to organize within the party to bend it. But in general, one side of the aisle tends to seem to have difficulty with finding enough common ground to actually work as a bloc, while the other side has managed, impressively, to unify Christian fundamentalists and ultra-rich billionaires.
The one that hasn't formed yet because the electorate has failed to recognize that parties only exist because they can consolidate mass political power. This is part of the "apathy" category. People don't care enough to meet up on this issue. They don't even care enough to be members of the existing parties or do more than show up to elections (and then, only between half and three-quarters for President, less for Congress, and hovering around 10-20% for primaries).
People care, but not enough to overcome institutional inertia.