For about 50 years the FBI was run by a paranoid lunatic named J. Edgar Hoover, a very sick man, a man whose instincts were anything but democratic in nature. I'm sure the organization that evolved under his guidance would make a superb Gestapo. All you would have to do is issue them the appropriate orders.

Team them up with the CIA and you would have the most efficient and deadly secret police outfit the world has ever seen.

All it takes is leaders with the will to do it.

The Constitution will avail you nothing under the rule of such people. Remember the McCarthy era and the HUAC? They could ask you anything they wanted in their kangaroo court, and you had to answer simply "yes" or "no" or else you were held "in contempt of Congress". They circumvented the Bill of Rights. They can do it. Only question is, will they?

If they do, plenty of ordinary people will cheer them on in the name of "national security" and "patrotism". I bet a majority would cheer them on or just stand silently by. That's what happened in Germany.