Emotional blackmail is a form of emotional abuse. Blackmailers rely on their victims being frightened of the consequences of not doing what they ask and on them losing sight of what is normal.
Emotional blackmail is a widely-used term, made popular by psychologists Forward and Frazier.
They identified that victims of emotional blackmail are usually stuck in a state of fear, obligation and guilt, and that these are the emotions blackmailers rely on for their blackmail to be effective.
Usually, the only way to escape from a relationship characterized by emotional blackmail is to leave, whether permanently or not. This can be very difficult, and potentially dangerous.