Environmental chauvinism? Explaining issue expansion among non-mainstream parties

Abstract

Do non-mainstream parties respond to other non-mainstream parties’ owned issues? Whereas a great deal of extant research has examined the owned issues of non-mainstream parties and when mainstream parties take on these issues, little research has been done to explore when non-mainstream parties expand their issue focus to include the owned issues of other non-mainstream parties. We argue that non-mainstream parties will expand their issue focus as the public salience on the issue increases, but that this expansion is conditioned by the type of issue. In particular, we posit that non-mainstream parties will expand on issues on which there is agreement among their supporters. To test our claims, we examine radical-left, radical right and green parties’ issue expansion on the environment and immigration in 15 West and East European countries from 1980–2018 using data from the Comparative Study of Electoral Systems, national election studies, and the Comparative Manifestos Project. Our findings have important implications for non-mainstream parties’ issue evolution and party competition more generally.