A new ad out tries to force McCain into that question pro-lifers never want to answer: if abortion should be a crime, how much time should women who have them serve? (Via)
I've yet to hear a coherent justification (at least, one that isn't nakedly paternalistic -- e.g., women are irrational creatures controlled by their emotions, so they can't be punished) for why abortion can be outlawed (as murder), but the murderers should get off scot-free. I suppose if someone doesn't think abortion is murder, but still can come up with a reason for it to barred, they could dodge out of this, but the few arguments I've heard on those lines are also pretty paternalistic (it's a serious decision, and we can't know if you're taking it seriously enough unless you're willing to prove it somehow to the state).
In any event, it's a question that McCain and his allies shouldn't be allowed to dodge. But I agree with Bean: it's a pretty new tactic (at least in mainstream argumentation), and nobody knows how new tactics will play out.