Are Niche Parties Fundamentally Different from Mainstream Parties? The Causes and the Electoral Consequences of Western European Parties' Policy Shifts, 1976–1998

<jats:p><jats:italic>Do “niche” parties—such as Communist, Green, and extreme nationalist parties—adjust their policies in response to shifts in public opinion? Would such policy responsiveness enhance these parties' electoral support? We report the results of statistical analyses of the relationship between parties' policy positions, voters' policy preferences, and election outcomes in eight Western European democracies from 1976 to 1998 that suggest that the answer to both questions is</jats:italic><jats:roman>no</jats:roman><jats:italic>. Specifically, we find no evidence that niche parties responded to shifts in public opinion, while mainstream parties displayed consistent tendencies to respond to public opinion shifts. Furthermore, we find that in situations where niche parties moderated their policy positions they were systematically punished at the polls (a result consistent with the hypothesis that such parties represent extreme or noncentrist ideological clienteles), while mainstream parties did not pay similar electoral penalties. Our findings have important implications for political representation, for spatial models of elections, and for political parties' election strategies.</jats:italic></jats:p>