Fed Power
I think that, empirically speaking, the evidence that our independent Federal Reserve system works well is pretty strong. The current combination of deep concern about an economic slowdown in a presidential election year does, however, remind us of how much power has been concentrated in an office with little political accountability. After all, one huge factor in November's election is just going to be what decisions Ben Bernanke makes about interest rates over the next few months. Insofar as he's worried about the medium-term risk of inflation, that's good news for the Democrats.
Of course, putting the Fed under tighter political supervision doesn't do anything to solve this problem. Still, it strikes me as an under-remarked-upon feature of our political system.