The conversion of continuing party activists to new policy positions plays an important role in the process of partisan change. Although a number of scholars have shown that conversion among continuing activists at the aggregate level contributes to overall ideological change within the parties, political scientists have devoted little attention to the factors associated with attitudinal conversion among individual activists. In this article, we develop a model of the individual-level conversion process and test it using panel data on the abortion attitudes of a national sample of continuing party activists. The results indicate that a number of factors distinguish those activists who convert as their parties' ideological positions change from those activists who do not. These factors include an activist's candidate preferences and general ideological orientations, the religious and political groups to which an activist belongs, the types of incentives that motivate an activist's political activity, and the political environment in the party in an activist's home state.
Party activists play a prominent role in the partisan change process. They often bring new issues into party politics (Carmines and Stimson 1989; Carmines 1991); they exert substantial influence on the selection of party candidates and the drafting of party platforms (Miller and Jennings 1986; Aldrich 1995); they influence the composition of government through their work in election campaigns; and they serve as "opinion leaders" in their local communities, shaping the images that the mass public forms of the parties' policy stances (Carmines and Stimson 1989). Thus, in order to understand the nature of political change in the United States, one must come to grips with change among party activists.
Scholars studying long-term change in the aggregate ideological stances of party activists often focus on the replacement of old party activists by new activists with different policy views (Aldrich 1983; Sundquist 1983; Carmines and Stimson 1989). Viewing replacement as the primary source of change seems logical given the permeable and candidate-centered nature of American party politics. When new candidates, touting new issues, emerge on the political scene, they attract a new set of activists, who find few barriers to entry into the party system. These new activists replace activists who were attracted to party politics by the candidates and issues of the past.
However, several scholars (Miller and Jennings 1986; Stone, Rapoport, and Abramowitz 1990; Rapoport and Stone 1994; Herrera 1995) demonstrate that partisan ideological change also results from the conversion of continuing activists to new policy positions. In some instances, the contribution of conversion to overall change is as great as or greater than that of replacement. This has important implications for the partisan change process. If conversion effects are in the same ideological direction as replacement effects, there will be either more overall change or more rapid change in the aggregate than if only replacement effects are at work. Moreover, continuing activists generally are more likely than newly mobilized activists to remain active in subsequent campaigns (Rapoport and Stone 1994). Thus, partisan change due in part to the conversion of continuing activists may be more likely to persist than change resulting only from replacement.
Given the significance of conversion, it is important not only to examine aggregate conversion levels, but also to ask a question that scholars have not addressed: Why do individual activists convert on an issue as the aggregate position of their party changes? On the one hand, there are some strong reasons why individual activists would resist conversion rather than follow intraparty trends. Activists hold their attitudes on issues with more conviction than do ordinary citizens and activists' attitudes are more stable over time than those of the mass public (Stone, Rapoport, and Abramowitz 1990). …