One of the ongoing debates among historians is whether a more durable left-wing coalition in post-WWI Germany could have prevented the Nazis from coming to power. I can’t resolve this question, but I contend that the failed anti-Nazi coalitions highlight challenges for left and left-leaning coalition-building in a damaged democracy. In particular, interwar history teaches us that a primary goal of coalition-building in the pursuit of social justice has to be the protection and strengthening of processes and procedures that allow deliberative democracy to persist. In this article, I look briefly at the formation and collapse of the interwar coalitions in Germany and draw some lessons from this historical example for US politics in the 21st century.