I would dismiss this as another nutty conspiracy - but it was reported by the BBC. From the link:
A BBC Radio 4 investigation sheds new light on a major subject that has received little historical attention, the conspiracy on behalf of a group of influential powerbrokers, led by Prescott Bush, to overthrow FDR and implement a fascist dictatorship in the U.S. based around the ideology of Mussolini and Hitler.This is one of those things that needs a Snopes article.
In 1933, Marine Corps Maj.-Gen. Smedley Butler was approached by a wealthy and secretive group of industrialists and bankers, including Prescott Bush the current President's grandfather, who asked him to command a 500,000 strong rogue army of veterans that would help stage a coup to topple then President Franklin Delano Roosevelt.
According to the BBC, the plotters intended to impose a fascist takeover and "Adopt the policies of Hitler and Mussolini to beat the great depression."