This article analyses how and why political parties adopt more restrictive migration policy positions by using Paul Sabatier’s Advocacy Coalition Framework. While a number of studies have emphasised electoral factors alone to explain this anti-immigration turn, this article argues that policies and cooperation constraints with organised interests are also fundamental factors to understand change in party positions about immigration policy. Using the Swiss case as an empirical application, the article shows how parties have sought to accommodate changing voter preferences with longstanding connections with organised interests. Centre-right parties have turned to an ever more restrictive stance on selective aspects of immigration policy (third-country migration, asylum, access to citizenship), however without challenging EU free movement so central for employers. Social Democrats have had to negotiate between the preferences of their middle-class voters keen on multiculturalism and those of trade unions whose base pushes for immigration control.