In California, a Not-So-Special Performance for Democrats, by Nate Silver. (The New York Times, 7/13/2011)
Excerpt: Ms. Hahn’s 9-percentage-point margin of victory, however, is underwhelming in a district where Democrats have an 18-point registration advantage.
But then I read this in the same paper on the previous day.
...in addition to the 12 percentage-point Democratic edge in voter registration in the district...
Of course, it also helps when you have deep pockets. Challenger Craig "Stop the Insaniity" Huey spent $900,000 of his own money, probably because the GOP paid him lip service only.