Abraham Lincoln, Franklin D. Roosevelt, and George Washington are most often listed as the three highest-rated Presidents among historians. The remaining places within the Top 10 are often rounded out by Theodore Roosevelt, Thomas Jefferson, Harry S. Truman, Woodrow Wilson, Dwight D. Eisenhower, Andrew Jackson, and John F. Kennedy. More recent Presidents such as Ronald Reagan and Bill Clinton are often rated among the greatest in public opinion polls, but do not always rank as highly among presidential scholars and historians. The bottom 10 often include James Buchanan, Warren G. Harding, Andrew Johnson, Franklin Pierce, Millard Fillmore, William Henry Harrison, John Tyler, Ulysses S. Grant, Zachary Taylor, and George W. Bush. Because William Henry Harrison (30 days) and James A. Garfield (200 days, incapacitated after 119 days) both died shortly after taking office, they are usually omitted from presidential rankings. Furthermore, Zachary Taylor died after serving as president for only 16 months, but he is usually included. In the case of these three, it is not clear if they received low rankings due to their actions as President, or because each was in office for such a limited time that it is not possible to assess them more thoroughly.
Political scientist Walter Dean Burnham noted the "dichotomous or schizoid profiles" of Presidents, which can make some hard to classify. Historian Alan Brinkley stated that "there are presidents who could be considered both failures and great or near great (for example, Nixon)". Historian and political scientist James MacGregor Burns observed of Nixon: "How can one evaluate such an idiosyncratic president, so brilliant and so morally lacking?"