What are the major difference between a positive ads and a negative one? I know if I run an TV ad on "I support War on Terrorism". Not only my rating on that issue will improve, but it will become a more important issue for voter. If I run an TV ads on "My opponet opposes War on Terrorism", the not only his rating will suffuer, but the issue will become less important. But what about the other two? The "I am against ....." and "Opponent is for ..."