1) Approval ratings for Mayor Fenty and School Chancellor Rhee have dropped significantly in 2 years.
2) DC residents see their city moving in the right direction in greater numbers than ever, and by significant increases in the last 2 years. This includes the perception of positive changes in the school system, widely regarded as a utterly broken two years ago.
It would appear that one can be popular, or one can govern, but not both. The question is why. This is not so simplistic a matter as 'voters are idiots, 'twas ever thus.' Voters have not always been idiots, and 'twas not ever thus. At significant times in our history we have been willing to sacrifice, and have had leaders who managed to both govern and remain popular.
I have some personal opinions, but they need more data. I suspect a confluence of trends rather than a single cause answer. Certainly the simple answers should be suspect.