Attempting to reconcile the diverse immigration policy demands of the ‘old’ working class and the ‘new’ middle class, social democratic parties struggle to take a clear position on immigration policy. Adopting more restrictive policies is a possible way forward, but this is likely to lead to electorally costly intra-party conflict. This article illuminates the conditions under which social democratic parties can unite behind more restrictive immigration policies and promote them consistently. Employing a most-similar systems design, it presents a comparative case study of the Austrian and Danish social democrats, from the 2015 ‘refugee crisis’ to 2020. The article argues that low levels of territorial decentralisation enabled the Danish social democrats to promote a restrictive stance on immigration top-down, while the Austrian social democrats’ federal party structure exacerbated internal disagreements between urban and rural leaders. These findings highlight the importance of internal party characteristics in explaining how parties respond to strategic trade-offs. Supplemental data for this article can be accessed online at: https://doi.org/10.1080/01402382.2021.1975211.