People still trust Bush more than Kerry with terrorism. I doubt that an attack would suddenly make swing voters think "well Kerry will fix this" and pull the lever for Hamster Boy and the Breck Girl.
And would they still if the Dems and their complicit media friends day after day showed another attack [God forbid] as being preventable had only Bush done xxxxxx or yyyyyyy? I have viewed this scenario as a wildcard for about three years now. I'm just not sure which candidate, if either, would benefit.
And I sincerely hope we don't get the opportunity to find out!