I've been trying to argue for some time that with two parties, even accounting for their primaries, the bandwidth of our representation is much too low to communicate a spectrum of political ideas. I forget the exact numbers I calculated, but from memory, current American democratic bandwidth at the national level is something in the neighborhood of 5 bits per year. This can't allow for any kinds of subtle distinctions between philosophy. We're stuck with big ugly buckets of loosely-related (at best) issues because we can't democratically communicate any more specifically.
I think this is somewhat true but not fully true. Elections aren't the only way in which policy gets communicated and so this bit-level analysis doesn't capture it fully IMO. If you look at border policy, for instance, Democrats have moved to the right not because of election mechanisms like primaries, but through public opinion.
