The flourishing of populist parties with an anti-immigrant stance have raised questions about the determinants of their success. A great attention has been devoted to the effect of immigration on the support for these parties all over Europe, but far less has been paid to the channels through which immigration is connected to this political success. We investigate these channels using a particularly rich dataset on Lombardy and taking advantage of the fortuitous coincidence of national and regional elections. We distinguish between the “ideological” anti-immigrant channel of the votes from two “rational” channels – crowding out of social services and competition on the labor market – arising from differences in economic features of immigrants with respect to Italians. After controlling for the ideological channel, our results suggest that economic factors play a significant role and that the competition on the labor market dominates the crowding out effect.