After each of the repeated mass shootings that now provide a tragic backbeat to American life, the same doomed dance of legislation quickly begins. As the outraged demands for action are inevitably derailed in Congress, disappointed gun-control advocates, and perplexed ordinary citizens, point their fingers at the influence of the National Rifle Association or the intransigent opposition of congressional Republicans. Those are both legitimate factors, but the stalemate over gun-control legislation since Bill Clinton’s first presidential term ultimately rests on a much deeper problem: the growing crisis of majority rule…