Probably no one has done more to analyze and clarify the psychological dimensions of contemporary politics than the psychiatrist, Dr. Bandy Lee. The ideas presented directly below are based on her ARTICLE LOCATED HERE. Perhaps the most important passage is the following: "Exposure to actual delusions is unlike exposure to strategic lies or simple misinformation; they are more infectious because the primary person is genuinely convinced of them."

Richard Koenigsberg
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SHARED PSYCHOSIS (Dr. Bandy X. Lee): The transmission of mental symptoms, Bandy Lee says, has been given different names: induced delusional disorder, shared psychosis, folie à deux, trois, quatre, or millions—depending on the number affected.

All describe the same phenomenon. Shared psychosis captures the syndrome-like severity, but is a misnomer because it often does not involve actual psychosis.  Folie à deux, or "madness in two," is perhaps the most preferred. The important feature is that mental symptoms are not confined to the person; they take hold and spread across interpersonal boundaries.

Severe psychopathology in an influential figure transmits to others or a group, until the exposed persons or groups come to feel, think, and behave as if they had the same disorder as the primary person. Exposure to actual delusions is unlike exposure to strategic lies or simple misinformation; they are more infectious because the primary person is genuinely convinced of them.