But the problem is, these probably comprise a minority of the electorate. Collectively, the majority of the electorate won't remember or care about it when the press is finished spinning. And even among those who remember, there are those who would still support Kerry no matter what he did or didn't do in Vietnam, or afterward. The only reason Kerry brings it up is to head off the criticism that Clinton got, and a warning to those who would try to paint him as someone who would be weak as a C in C in the WOT.
Remember that the press sold Clinton to the sheeple even though he was on record as a draft dodger and one who "loathed" the military. The Rats and the press spun it was unimportant or, worse, something to be held in his favor (e.g., "a man of conscience"). When you support a person on strictly ideological grounds, character, or lack thereof, assumes, at best, secondary importance.