A1HR.org advocates the enactment of a Public Law that caps Congressional Districts at 50,000 citizens, as proposed by the original first amendment in the Bill of Rights known as Article the First. This law would neuter lobbyist HR influence, invalidate Gerrymandering, rectify the Wyoming vs California Electoral College imbalance, greatly reduce the cost of HR races and thus restore the collective wisdom of citizen governance over the House of Representatives.
I don't believe that 50K per district is magic. Why not more or less? But 700K is totally unacceptable in a nation that is to be controlled by its people.