American politics is structured as a competitive game, so there will always be those who will look for an opening to make their side look good, or to besmirch the opposition. We filter the policy pronouncements of our leaders by what we know of their character. Yet political reputations, as George Bush can tell us with chagrin, can fluctuate rapidly. While a politician is active, his reputation can be burnished by his actions and the attentions of his friends, or can be smeared by the activities of his cronies. Eventually, after politicians, their agents, and their enemies have left the scene, historians take their turn in solidifying presidential reputations, writing the textbooks that teach students which leaders deserve honor.
Historians have great weight in shaping our collective memory.
Indeed, since the realignment of the parties in 1856, Democratic presidents have fared better with historians than Republicans. Of the Republican presidents only Lincoln, Teddy Roosevelt, and Dwight Eisenhower are rated above average in polls of historians. To understand the power of reputations, consider the president perceived to be America's worst leader. That president, judged by the evaluations of the public and historians, is Warren Gamaliel Harding. Yet this reading, widely accepted today, contrasts mightily with how contemporaries viewed Harding.