Is a monopolized banking sector a threat to democracy? Increasing bank monopolization and its growing share of the economy have brought renewed interest to this historical concern. Oskar Lange and Abba Lerner held that banking monopolization would undermine democracy through the concentration of political power among banking elites. This led them to exclude the banking sector from their more general support for private ownership of the means of production. We examine whether banking monopolization is associated with concentrated political power and the undermining of democracy using the Lerner Index (based on Lerner’s measure of banking concentration), Polity scores, Varieties of Democracy’s (V-Dem’s) Political Civil Liberty Index, and V-Dem’s Power Distributed by Socioeconomic Position Index, comprising data for 101 countries from 1996 to 2014 in our full specification. We find no relationship between civil liberties and the banking sector in Organisation for Economic Co-operation and Development (OECD) countries but a negative and statistically significant relationship in non-OECD countries. We find no relationship between the Lerner Index and the concentration of power by socioeconomic status. Our results support only one variant of the Lange–Lerner Hypothesis and only among non-OECD countries. We argue that, most likely, this is because long-established democracies are more resilient.