Editor's note: CNN Contributor Bob Greene is a bestselling author whose 25 books include "Late Edition: A Love Story" and "Once Upon a Town: The Miracle of the North Platte Canteen."
(CNN) -- As rooms go, it's quite nice.
It's shaped like an egg. It has a well-tended garden a few feet out the door, and then an expanse of lawn leading to a fence.
It is certainly not the most ornate or luxurious room in the United States. Most five-star hotels have suites that out-glitter it. Any number of corporate CEOs boast offices that are larger and more lavishly outfitted.
But the Oval Office at 1600 Pennsylvania Avenue in Washington has always been the object of a singular kind of yearning. Mitt Romney fervently wants to move into it in January; Barack Obama just as fervently wants not to move out. This fall's presidential campaign, which begins in earnest with the Republican National Convention this week, will determine whether it will be Romney or Obama who gets his wish.
Campaigns go by so quickly, and unfold so feverishly, that the combatants can be excused for not dwelling on the fact that each successive occupant of the Oval Office is, by definition, a transient.
It's temporary work, the presidency, and the Oval Office is the traditional home of the most high-level temps in the world.
I've been looking at two pieces of Oval Office video, each mesmerizing, even astonishing, in its own way. Neither was originally intended for public consumption. Each stars a man who is in his final weeks -- or in one case final hours -- as president.
One of the men knows it. The other has no idea.
The first video consists of outtakes from an interview that Chet Huntley and David Brinkley of NBC News conducted with President John F. Kennedy on September 9, 1963. Huntley and Brinkley were at the apex of their fame and journalistic influence; their evening newscast, "The Huntley-Brinkley Report," was expanding from 15 to 30 minutes, and Kennedy had agreed to tape the Oval Office interview to launch the longer show.
The main interview had concluded. But on the tape, Kennedy tells Huntley and Brinkley that he is dissatisfied with some of the answers he gave them. He wants to do them over.
"There's one or two places we're a little ragged," he says to the newsmen.
And then, to be certain Huntley and Brinkley understand what he is asking for:
"Let's try and do it again and we'll see what comes out this time."
They accede; they redo the questions. And what comes across most strongly in the footage is the complete aura of command that Kennedy projects in that White House office. He appears filled with the Oval Office's inherent power and authority, and betrays not a smidgen of doubt that, for him, all of that will likely go on.
Neither Kennedy, nor Huntley and Brinkley, could have had any inkling that within 12 weeks he would be dead in Dallas, that the two newsmen would be covering his funeral, and that Lyndon Johnson, not he, would be sitting in this office. In the outtakes, Kennedy gives Brinkley advice on whether a new Cary Grant-Audrey Hepburn movie is worth seeing; Kennedy seems supremely at home and at ease in that room. Leaving it looks to be the furthest thing from his mind.
The other piece of videotape features a president who knows that, within 24 hours, he will be leaving the Oval Office, and the presidency, ahead of schedule.
Most of us have seen Richard Nixon's resignation speech from the evening of August 8, 1974. But, in the five minutes before he addressed the nation, there was some calibrating of lights and checking of sound levels. Nixon was in the chair behind his desk for that. And it was all being recorded.
Through the amalgam of overwhelming emotions that had to have been coursing through him -- he knew what he would be saying to the citizens of the United States a few minutes later -- Nixon grins. It is as if he does not want the technicians to see his anguish
To an assistant who, for purposes of lighting adjustments, is sitting in the president's chair behind the Oval Office desk as Nixon enters the room, Nixon says: "Hey, you're better lookin' than I am. Why don't you stay here?" To the person operating the television camera: "Have you got an extra camera in case the lights go out?"
It's banter, in a dark American hour. He sit behind his desk and says: "All Secret Service, are there any Secret Service in the room? Out."
He gets no response, and because the camera is focused on Nixon we don't see the Secret Service agents. But it is clear that they do not depart, because Nixon says in their direction:
"You don't have to stay, do you?"
"You're required to?"
"I'm just kidding you."
It is a difficult video to watch, because the moments are so raw. In its own way, it is even more revelatory than the resignation speech itself. Here is a man who worked all his life to make it to this room, and now he -- as Kennedy, in a very different context, did before him -- is leaving it earlier than he thought he would have to.
Kennedy and Nixon may be the stars of those videos, but the real star is the room itself -- it is the one aspect of the videos that is sustaining and permanent. Mitt Romney and Barack Obama will battle all fall for the symbolic key to that room, even while knowing that, in the end, it will stop being theirs.
Presidents depart; the Oval Office remains. Which may be at the heart of the lure that has made so many people over the centuries hunger to be there, for however brief or long a stay.
Follow us on Twitter @CNNOpinion
Join us on Facebook/CNNOpinion
The opinions expressed in this commentary are solely those of Bob Greene.