In this research, we examine the role of attachment to an ideological group as a source of stability in a volatile multi-party system. In two studies conducted in Israel (N=1,320), we show that a multi-item Attachment to an Ideological Group (AIG) scale is strongly tied to vote choice and political engagement, and its effects are independent of, and more powerful than, issue-based ideology and partisan identity strength. Compared to individuals with a weak ideological attachment, those who score highly on the AIG scale are more likely to vote for a party from their ideological camp and participate in politics. Moreover, in two survey experiments, respondents high in AIG displayed stronger anger or enthusiasm—known harbingers of political action—in response to threat or reassurance to their ideological group’s status, attesting to a link between AIG and political engagement. Our ﬁndings underscore the importance of ideological group attachments in a volatile multi-party system.