about FDR
It was eighteen years after he died before a couple of academics revealed the real cause of the depression (http://press.princeton.edu/titles/746.html). That opened the gates for other economic historians to conduct an epidemiological analysis of his endless stream of errors.
No matter. The Depression was a scarring experience and this clown was seen as doing something! to alleviate the pain. That hero status was embedded in the national consciousness and remains common even today.
Amity Shlaes has a pretty good compilation of subsequent analysis in THE FORGOTTEN MAN. Worth the read.