Air pollution caused by traffic and other sources remains a challenge in big cities and urbanized areas in Germany and abroad. Nitrogen dioxide emissions, particulate matter, noise emissions, and ozone are still problematic issues with negative impacts on both the environment and human health. In 2018, the German Federal Government launched the “Lead City Program,” a €130-million fund to support five selected so-called Lead Cities in developing and implementing air quality policies. This article comparatively analyzes the policy-making process and policy content for better air quality in the three (out of five) Lead Cities—Essen, Herrenberg, and Reutlingen. Conceptually, we rely on two theoretical frameworks—the policy package approach (PPA) and the multiple streams framework (MSF). The objective, thus, is an ex-post analysis of policy development by means of two policy science-based concepts. Based on document-based desk research and qualitative interviews with policymakers and stakeholders in each of the three cities, we identified a number of key variables that created a window of opportunity and paved the way for the selection of the policy packages. The resulting five key variables are direct interaction between the different governance levels, long-standing non-compliance with the European Union (EU) NO2 limit values in many German cities, the resulting European and national infringement proceedings, the diesel scandal, and the Lead City Program as overall multiple stream-coupling facilitators. The results are then discussed regarding the explanatory power of MSF and PPA and the mutual potential linkages these concepts offer for future research.