Research that the Office of Strategic Services/CIA declassified some years ago, available at the National Archives: "A Psychological Analysis of Adolph (Adolf) Hitler: His Life and Legend," by Walter C. Langer. From this:
"His primary rules were: Never allow the public to cool off; never admit a fault or wrong; never concede that there may be some good in your enemy; never leave room for alternatives; never accept blame; concentrate on one enemy at a time and blame him for everything that goes wrong; people will believe a big lie sooner than a little one; and if you repeat it frequently enough people will sooner or later believe it."
More from his deputy, Hermann Goering:
"The people can always be brought to the bidding of the leaders. That is easy. All you have to do is tell them they are being attacked and denounce the pacifists for lack of patriotism and exposing the country to danger. It works the same way in any country."