They can no longer claim to know about the fakes, because they used them to their advantage.
That is a great logic point that I hadn't thought of, but here is where that probaby falls down, though. The sKerry campaign hasn't "explained" anything, from Christmas in Cambodia to "I voted for it before I voted against it". The upside would be that it would be another nail in Jenjis' coffin (how many nails can you put in a coffin?).