There are a number of reasons that people lie. The first is fear. This is the most common reason that people may lie, and they are taking shelter from a perceived punishment. It may be because they know they have done something wrong a single time, in which case it is not compulsive lying. But if they are always in fear of being punished, it may become a habit, which is a second reason for lying. In this case, it may become compulsive lying, which is lying by reflex. Even when confronted by the truth, they insist the lie is the truth in this case. A third case is learning to lie through modeling. When a people see others lie, especially when they get away with it, they may become more prone to lying. Finally, people lie because they feel if they tell the truth they won't get what they want. Thus, out of the main reasons for lying, only lying by habit can truly be called "compulsive lying."
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http://www.mental-health-matters.com/articles/article.php?artID=153>
I believe our opposition has a mental health issue to deal with. I can name many Repubs who i truly believe may have this condition.