A reader dissents from my take:

While I generally agree that attacks tend not to stick unless they reinforce something people already believe -- i.e. Kerry's windsurfing comports with people's view that he's a northeastern elitist, I think the significance of the houses story is that it helps defang a storyline McCain wants to use against Obama.... Obama won't successfully paint McCain as a rich elitist, but McCain now knows that every time he tries the same tactic against Obama he has to hear about all his houses again.

--Michael Crowley