I have no idea he is doing that, but the fact remains, it won't stop other members of the liberal establishment from keeping the issue alive. Kerry was pounding Bush on this issue just yesterday. I see no evidence that Kerry intends on halting his attacks against Bush on this specific issue in public speeches.
I seem to recall that the Kerry campaign continued to harp on the National Guard thing long after the CBS docs had come into serious question. Let them yap on about it.