As I said, the question is how you escape the "local optimum" given that you are in it. Clearly neither parties have any interest in changing up the current electoral system.
Most election rules in the US are set by states, many states (including the largest) have a citizen initiative process. Support by incumbent politicians is not necessary for reform that provides proportional representation with candidate-centered elections (e.g., STV rather than something like party-list-proportional) at the state level, which can provide the basis for creating pressure for the necessary federal reforms (e.g., modifying the federal statutory prohibition on multimember congressional districts -- created to stop the practice of states using multimember winner-take-all districts to avoid minority representation -- to allow multimember districts using methods that produce proportional results like STV) to at least allow states the option of providing better methods of electing federal representatives.
