Results of research funded by the Improving Campaign Conduct grant supported by the Pew Charitable Trusts.

1. Introduction / David A. Dulio, Candice J. Nelson, and James A. Thurber -- 2. Effectiveness of negative political advertising / Richard R. Lau and Lee Sigelman -- 3. Eliminate the negative? Categories of analysis for political advertisements / Kathleen Hall Jamieson, Paul Waldman, and Susan Sherr -- 4. How negative campaigning enhances knowledge of Senate elections / Kim Fridkin Kahn and Patrick J. Kenney -- 5. Agenda setting and campaign advertising in congressional elections / Paul S. Herrnson and Kelly D. Patterson -- 6. "Basic rule" voting: campaign impact on party- and approval-based voting / Shanto Iyengar and John R. Petrocik -- 7. How issue ads have reshaped American politics / Darrell M. West -- 8. Summary and conclusions / David A. Dulio, Candice J. Nelson, and James A. Thurber.