As I've decried before, the charge that a politician "flip-flops" is, at best, useless and, at worst, an active condemnation of the ability to change one's mind, a characteristic we should want in our leaders. Via Tapped, I found this Richard Cohen column that discusses how Bush has flip-flopped in pointing out the ridiculousness of this particular form of political gotcha:
Flip-flopping, like beauty, is in the mind of the beholder. It can be an indicator of an alert mind, one that adjusts to new realities, or it can be evidence of ambition decoupled from principle. With Kerry it's a mix of both. With Bush, who changes his positions but never his mind, it is always the latter.
As you can probably tell from this passage, the article is particularly unfriendly to Bush. In fact, the impetus behind the column seems to be criticizing Bush rather than the idiocy of "flip-flop" claims, but in the process Cohen makes some good points on both topics.