This article examines recent attempts to create a common European Union (EU) immigration policy. This “harmonized” policy has faced political blockages, despite being seen by most observers as necessary if the EU is to meet its goal of free movement of labor. Because of this resistance, immigration harmonization has lagged behind other EU policy areas. To explain national resistance to harmonizing immigration policy, our article develops a theoretical and conceptual model of how immigration policy is potentially harmonized at the EU level, but how this harmonization can be blocked or restricted. We explain these political blockages with a model of intergovernmental bargaining that focuses on political salience, political partisanship, and institutions that protect immigrant rights. We argue that these national-level factors have determined the success and the nature of various harmonization proposals, by determining the positions of member states when negotiating in the European Council. Our primary hypothesis is that when the political salience of a given immigration issue is high, any harmonization that results is more likely to be restrictive toward immigrant rights. We also hypothesize that the impact of institutions that protect immigrant rights, and of political partisanship, is variable depending on the issue area and the national context. We use literature on European integration, immigration politics, agenda-setting, venue-shopping, and two-level games to theorize, operationalize, and test these hypotheses. The article helps to advance scholarly work on immigration politics, but our model could also conceivably be applied to other high-salience policy areas in the EU.