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general::
Distrust of a public statement or position, as in The current credibility gap at City Hall is the result of miscommunication between the mayor's office and the press. This term originated about 1960 in connection with the American public's disinclination to believe government statements about the Vietnam War. It soon was extended to individuals and corporations as well as government agencies to express a lack of confidence in the truth of their statements, or perception of a discrepancy between words and actions.
American Heritage Idioms