Kerry Tries to Counter Impact of Criticism WASHINGTON - Attacks on John Kerry's war record may be beginning to have an impact, polls suggest, amid raised voices and new TV ads on a subject at least temporarily dominating debate in the close presidential race.    Democrats are laboring to deflect the questioning of Kerry's record with fresh ads touting his fitness for national command, even as the White House mocks the Massachusetts senator as "losing his cool" over claims he lied to win military medals in Vietnam...