When the President starts lying he begins to need evidence to back up
his lies because in this democracy he is questioned on his statements.
It then percolates down through the bureaucracy that you are helping
the Boss if you come up with evidence that is supportive of our public
position and you are distinctly unhelpful if you commit to paper
statements that might leak to the wrong people.

 The effect
of that is to poison the flow of information to the President himself
and to create a situation where a President can be almost, to use a
metaphor, psychotically divorced from the realities in which he is
acting…
– Daniel Ellsburg to the US Senate on Foreign Relations, May 13, 1970

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“The
most brilliant propagandist technique will yield no success unless one
fundamental principle is borne in mind constantly…it must confine
itself to a few points and repeat them over and over.
– Joseph Goebbels, Nazi Propaganda Minister