<p>John Kerry mentions his service in Vietnam so frequently that it has become a running joke on the campaign press plane. He seldom if ever mentions his postwar activities as a national coordinator and principal spokesman for Vietnam Veterans Against the War, a group he says he quit in 1971 because he was concerned about its radical agenda. One reason may be that a credibility gap has started to widen over his antiwar history, and he clearly doesn't want to discuss it at length. His campaign is issuing misleading and evasive statements on his antiwar service in a way that would do the Pentagon spinners of the Johnson and Nixon administrations proud.</p>