I think that most historians would agree that history gets rewritten all the time. They might go further and say that history must be rewritten by each generation. For many people, this is a hard thought to grasp but each generation rewrites history in terms of its interests, beliefs and the way things worked out.Those Mudcatters who are old enough can remember this happening. During and directly after his presidency, Eisenhower was regarded as a somewhat limited man, intellectually, partially because he had unusual speach habits, but the more we learn about his Presidency and see how his ideas helped to shape what came after, the more he is appreciated. His warning of the growing power of the military industrial complex (and I believe he coined that term) rings true today. Truman, I think it is safe to say has risen in the estimation of Presidential historians (and they are the ones who shape opinion by their books directly and by their teaching)from mediocre to one of the most successful and important presidents of his century.
It works the other way too. John Kennedy has been sinking in the estimation of many historians. His personality shines bright as do his ideals but his importance is being re-evaluated. His treatment of women, valued in our time as a touchstone in a way that would have been inconceivable in 1960 is probably a part of this. James Garfield was considered at the time of his death to be up there just under Lincoln. Now most people would be hard-pressed to name two achievements of a man who was regarded as one of the great presidents of the 19th century.
History gets re-evaluated in the light of the interests of the society of that generation. If there is a swing to conservatism in society as a whole, those presidents who exemplify the ideals of that point of view are going to rise up in degree of appreciation. This does not mean that facts change, just that emphasis changes.
This is different than historical revisionism in a totalitarian country where once great leaders become non-persons, erased from history books because they no longer fit in with the needs of the present ruler of the country. Under such academic constraints, where people from the past have been rewritten from history, it is impossible to study the new vesion of history and learn how the present evolved from the past. The lessons of history are lost to that society and it will pay a price.
Sourdough