How US leaders can best support protesters in Iran

Democracies tend to be more effective in speaking to their own people than in communicating with foreign audiences. Part of the reason is that public diplomacy, the practice of engaging and informing the people of other nations, is still considered an elite practice confined to the marble halls of the State Department and foreign ministries.

But public diplomacy — because it is so people-centric — can make the difference between long-term peace and global upheaval.

The death of 22-year-old Mahsa Amini for wearing an “inappropriate hijab” has sparked mass protests from...