AdvertisementDo Negative Ads Make A Difference? Political Scientists Say Not So MuchApril 03, 2012Shankar VedantamfacebookEmailFuture U.S. senator and presidential candidate John Kerry poses with crewmates during the Vietnam War in this file photo. An attack on his service by a group calling itself the Swift Boat Veterans for Truth is remembered as a turning point in the 2004 election. But political scientists say negative ads might not be that effective. (AP)