"The awful question is: Why can’t we, or why won’t we, do anything about a system that presents us with two of the worst candidates in memory?"
Because collectively, we're too damn lazy to fulfill our civic responsibilities.  We don't make the time or put forth the effort to understand how our system of government works, who the candidates really are (and who is behind them), the issues of the day, our history, etc. We think by waving the flag, putting a "Support the Troops" bumper sticker on our car, and voting in November that we have fulfilled our civic duty - BULL.  We've become too self-indulgent, distracted, and preoccupied with living "the good life", and are not willing to make the sacrifices necessary to maintain a government "of, by, and for the people". The failure of our political system rests squarely on our shoulders and, as much as we point fingers and whine about whose fault it is that our country is in the shape it is, we have no one to blame but ourselves.