As the Swift Boat Veterans for Truth previewed another ad to air next week, a survey released yesterday said their first controversial attack on John F. Kerry's war record reached more than half the nation with the help of a media buzz created by talk radio and cable news. The first spot, which began airing Aug. 5 and ran only in West Virginia, Ohio, and Wisconsin, triggered a counterattack on several fronts this week. On Thursday, Kerry accused the veterans of doing President Bush's campaign's "dirty work." A front-page story in yesterday's New York Times raised questions about the credibility...