Critics of johnson's policies in vietnam used this term to describe their distrust of what the johnson administration reported to the public about the war.

The correct answer is Credibility Gap

This was used because of the way Johnson and his administration talked about the Vietnam war which was against of what they were doing at the time in Vietnam and how they were resolving the issue. Basically, it was a euphemism used by the media to describe that Johnson and his people were lying about the war.