The Vietnam War had a major impact in shifting public opinion toward distrust of government. During the Vietnam War, a major CREDIBILITY GAP became apparent in regard to what the government was telling the American public vs. what was actually taking place. The term "credibility gap" was used by journalists who questioned the optimistic picture that the Lyndon Johnson administration painted regarding how the war was going, when investigative reporting showed a much more negative reality.
The credibility gap grew even larger when the Pentagon Papers (classified documents) were leaked to the press in 1971, showing that the government indeed had been deceiving the public about the plans and conduct of the war over the years.