As someone who has more than a passing acquaintance with most of the 20th century presidents, I have often thought that their accomplishments have little staying power in shaping popular views of their leadership.
William Henry Harrison, who died of pneumonia in April of 1841, after only one month in office, was the first Chief Executive to hide his physical frailties.
Once the public loses confidence in a president's leadership at a time of war, once they don't trust him anymore, once his credibility is sharply diminished, how does he get it back?
One doesn't simply write about Lyndon Johnson. You get the Johnson treatment from beyond the grave - arm around you, nose to nose. I should admit that he also reminds me of my father, quite an overbearing and narcissistic character. And in some ways, he reminds me of myself. Another workaholic.
Ronald Reagan in foreign affairs, I think, was someone who had certain, very general ideas, general propositions by which he lives: To combat communism, to build up the American military power to assure our national security against any conceivable threat.
There are examples of ex-presidents speaking out. Jimmy Carter has not held back on a variety of issues. Harry Truman didn't.
The Cold War is over. The kind of authority that the presidents asserted during the Cold War has now been diminished.
Lyndon Johnson is not a comfortable model for President Obama to imitate. He is an all-but-forgotten president - pilloried for the failed war in Vietnam and criticized for grandiose reforms conservatives denounce as the epitome of federal social engineering that costs too much and does too little.
The 1890s was an intensely patriotic decade for Americans. It was a time of neo-imperialism, when the European powers and the United States were establishing their flags around the globe.
At the end of the day, Americans are not so keen on ideologues, people who have such fixed positions that they can't see any virtue in the other side's point of view.
Clinton's egregious act of self-indulgence was outdone by an impeachment based not on constitutionally required high crimes and misdemeanors but on a vindictive determination to bring down a president who had offended self-righteous moralists eager to put a different political agenda in place.
Vietnam was a palpable failure. And of course, in retrospect, it was even more clearly a disaster and a failure than maybe people understood at the time.
True, most Americans give lip service to the proposition that even the most exalted among us have their flaws, but we are eager to believe that presidents manage to rise above the limitations that beset the rest of us.
When Johnson decided to fight for passage of the law John F. Kennedy had put before Congress in June 1963 banning segregation in places of public accommodation, he believed he was taking considerable political risks.
F.D.R. had an economic crisis of unprecedented proportions in 1933 when he drove 15 major bills through the Congress, and super majorities in the House and the Senate in 1935 when he won passage of Social Security.
Historians will look back and say, 'Foreign policy in the Ford presidency was very much dominated by Kissinger, with a kind of continuity from the Nixon period.' Ford is not going to be remembered as a really significant foreign policy maker.
The CIA's official history of the Bay of Pigs operation is filled with dramatic and harrowing details that not only lay bare the strategic, logistical, and political problems that doomed the invasion, but also how the still-green President John F. Kennedy scrambled to keep the U.S. from entering into a full conflict with Cuba.