By Richard Reeves - August 30, 2008

DENVER -- Is Barack Obama prepared to be president? No. Neither is John McCain.

I have written about 12 pounds of books on the presidency over the past 22 years, three long studies that focused on the day-to-day work of John F. Kennedy, Richard Nixon and Ronald Reagan. This is the most important thing I learned in doing that, a paragraph at the end of the introduction to "President Kennedy: Profile of Power":

"John F. Kennedy was one of only 42 men who truly knew what it is like to be president. He was not prepared for it, but I doubt that anyone ever was or ever will be. The job is sui generis. The presidency is an act of faith."

The Kennedy book was published during the presidency of Bill Clinton, so now 43 men know. Obama, as I said, is obviously not one of them. But in praise of his acceptance speech here after winning the Democratic nomination, I did think the senator from Illinois, four years older than Kennedy was when he was inaugurated, showed he had a clue when he said:

"We need a president who can face the threats of the future, not keep grasping at the ideas of the past."

That is not a particularly graceful or articulate line, but it is the most important fact about being president. The toughest job in the world is essentially reactive. The president does not run the country and is not paid by the hour. He is there to respond to events unanticipated: bizarre attacks on New York City, the blockade of a European city occupied by American troops, the rising of young black men and women against legal segregation, civil wars and genocides in places we never knew existed, the shelling of an American fort off South Carolina by other Americans.

Presidents are alone, facing the unknown. The job is not about running the country; it is about leading the nation in unexpected crisis or danger. No one remembers whether Lincoln balanced the budget.

Obama touched on what we anticipate will be the issues faced by the next president, as McCain will this week: a fading economy and place in the world, terrorism, health care, climate change. All important, critical, even, but no one knows what will be the issue that defines the next president. John Kennedy and Richard Nixon debated about defending Quemoy and Matsu, two islands off what we then called "Red China," but Kennedy's presidency was defined by surprising events in the Cold War against communism, and by civil rights and a civil war in what was called French Indo-China.

And if you are interested in what being president is like, look at the day 45 years ago, Aug. 28, 1963, when Martin Luther King Jr. gave his "I Have a Dream" speech on the steps of the Lincoln Memorial. That made Kennedy realize that his historical destiny would be to put the government on the side of a minority, no small thing in a democracy of majority rule. Until that day, Kennedy had never allowed himself to be photographed with King, who was seen, rather suspiciously, as a man of the left.

That day, he invited the black minister to the White House. Waiting for King to arrive, Kennedy met with the National Security Council and signed off on a plot to depose President Ngo Dinh Diem of South Vietnam, an action that turned that far country into an American military colony -- an action that led to disaster.

That is what it was like to president. No one, least of all Kennedy, knew. In the end, we choose a president on our own sense of character and judgment. In the end, it is not about the candidate; it is about the character and judgment of the American people. We decide. It is a great gamble. Then, the president's real job is to bring out the best in us.