The idea that governments should forbid behaviour that is morally wrong is the element of modern democracy that is most closely related to Judeo Christian principles.
Explanation:
The religions of Judaism and Christianity mostly share common values and beliefs. If not clearly identical, they are very similar to each other. The idea of morality in both religions allows it to propose in their teaching to abandon any behaviour that doesn't fit their idea of morality.
Their idea of morality is simple. It says that anything that causes anyone harm is immoral.