In this paper we investigate with a survey experiment and a field experiment on Twitter how much political polarization is driven by anti-immigration narratives that have a negative depiction of the migrants. Furthermore, we look at how much this depends on private preference or on how these narratives are publicly endorsed. We confront these narratives with other ones: either hostile or in acceptance of migration with an emphasis either on the out-group, on the in-group or on economic reciprocity. We find that indeed political polarization is driven by the emphasis of the narratives. On Twitter the out-group emphasis drives polarization and the corresponding anti-immigration narrative is the only
one going viral. In the survey right-wing participants prefer the reciprocity emphasis more, but we still find evidence of more polarization when allowing them to go public.