Can Obama Go In For The Kill?

It's part of the frustration on the part of his supporters and some scorn from the skeptics: in the debates and even in his advertizing, Obama doesn't seem to have a killer instinct. In the last debate, for example, on the one issue where he was all but invited to pile on in criticizing Clinton, on her Bosnia lies, he actually defended her. Clinton was not so restrained, in the same position. One viewer's take:

I asked my 82 year old mother, who hates politics with a passion because it is so negative, what she thought about the debate.  She said "Well, he's being a gentleman, of course.  Thank goodness, that is why I will vote for him."  She then said "It's about time someone behaved properly."  She then also asked me why I was making her watch the coverage.  "You know this is why I hate politics, I'm going to go play mahjong on the computer."

I just hope he doesn't go negative with McCain. A key to his appeal is his positive reason, which would be revealed as mere cunning if it did not apply to running against Republicans as well.