Via Ambinder, Walter Shapiro says that "Every time Obama takes off the gloves, he immediately feels compelled to lace them up again." This is such a frequently used metaphor that it had never occurred to me to think about what it's specifically referring to. But that makes sense: boxing gloves. The problem is that, as I understand it, you can actually do more damage to someone wearing the gloves, since the gloves primarily serve to protect your hand while still letting you inflict incredible head-trauma on your adversary.
If I were a more clever writer, I'd now explain why that's exactly like Obama's campaign strategy but the boring truth is that he seems to be hoping that John Edwards' aggressive attacks on Clinton will wind up doing his job for him (and he just might be right).