Not about Huey Long
One thing I hate is when people believe so strongly in the reader/viewer oriented style of interpretation that they ignore the author or a work. The author of this book came out openly and said that he did not intend his book as a perspective on Huey Long. Warren can obviously express himself better than I can:
"One of the unfortunate characteristics of our time is that the reception of a novel may depend on its journalistic relevance. It is a little graceless of me to call this characteristic unfortunate, and to quarrel with it, for certainly the journalistic relevance of All The King's Men had a good deal to do with what interest it evoked. My politician hero, whose name, in the end, was Willie Stark, was quickly equated with the late [US] Senator Huey P. Long....
This equation led, in different quarters, to quite contradictory interpretations of the novel. On one hand, there were those who took the thing to be a not-so-covert biography of, and apologia for, Senator Long, and the author to be not less than a base minion of the great man. There is really nothing to reply to this innocent boneheadedness or gospel-bit hysteria. As Louis Armstrong is reported to have said, there's some folks that, if they don't know, you can't tell 'em... But on the other hand, there were those who took the thing to be a rousing declaration of democratic principles and a tract for the assassination of dictators. This view, though somewhat more congenial to my personal political views, was almost as wide of the mark. For better or worse, Willie Stark was not Huey Long. Willie [Stark] was only himself....
[T]he difference between the person Huey P. Long and the fiction Willie Stark, may be indicated by the fact that in the verse play [Proud Flesh] the name of the politician was Talos — the name of the brutal, blank-eyed 'iron groom' of Spenser's Fairie Queene, the pitiless servant of the knight of justice. My conception grew wider, but that element always remained, and Willie Stark remained, in one way, Willie Talos. In other words, Talos is the kind of doom that democracy may invite upon itself. The book, however, was never intended to be a book about politics. Politics merely provided the framework story in which the deeper concerns, whatever their final significance, might work themselves out."
He also did not intend the book as a commentary on politics either, the story is simply the story, nothing less and nothing more. Personally I think his work in stronger because it is not an attempt to be relevant to the modern politics of any age, but instead talks about human nature. If Warren were attempting to comment on the politics of his age, it is possible that his work would be forgotten now. Love it or hate it, at least interpret it correctly.