My paper seeks to identify the conditions under which the European Union (EU) can successfully leverage its legal and normative authority to enforce its binding democratic principles. By drawing on recent cases of serious democratic backsliding in Hungary and Poland, I offer possible explanations for why the EU might fail to act on clear violations of its binding democratic principles among member states. Conversely, I consider the cases of Croatia and Turkey, in which the EU has more stringently enforced democratic practices as a condition of EU membership, and I examine why they were able to do this. My paper finds that historical predispositions toward EU integration and the principle of conditionality allow the EU to facilitate democratization in candidate member states (Croatia) and to exclude increasingly undemocratic candidates (Turkey) from membership. Meanwhile, geopolitical considerations and fears over anti-EU backlash have slowed EU action against increasingly authoritarian policies in existing member states, such as Hungary and Poland. Drawing on theoretical explanations of action or inaction on the issue of democracy protection, I advance practical understandings of why democratic erosion can be stopped in some cases but not others. The dynamics of increasingly authoritarian developments in Hungary and Poland - and the lack of domestic mechanisms to reverse them - have thus far been well-documented in the literature. However, a concrete analysis of what the EU can do to help in these circumstances - and what influence the EU has had in candidate states such as Croatia and Turkey - is still underdeveloped in the literature. As such, my paper will attempt to outline and contextualize the various considerations faced by EU institutions when interacting with democratic backsliders and crafting a response to their actions. This paper will be presented at the European and Euasian Undergraduate Research Symposium at the University of Pittsburgh in April 2018.