one problem with the prediction that future generations will look favorably on his prezzziduncy: they will all be dead

News item: Citing History, Bush Suggests His Policies Will One Day Be Vindicated

As the door begins to close on his tenure, Bush is increasingly drawing on selected events of the past to argue that history will vindicate him on Iraq, terrorism, trade and other controversial issues.
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White House aides say Bush, who majored in history at Yale, likes to emphasize historical comparisons because they are easy for the public to understand and illustrate in dramatic fashion how differently future generations may come to view him.

Unfortunately for the president, many historians have already reached a conclusion. In an informal survey of scholars this spring, just two out of 109 historians said Bush would be judged a success; a majority deemed him the "worst president ever."