In my years as a newspaper reporter, the best story I never wrote was about John McCain.

It was in Saigon, in late fall of 1974. The last U.S. troops had left early the previous year and American prisoners of war had been freed, but the war ground on, with both Vietnamese sides ignoring the cease-fire that was supposed to end it.

McCain, a former POW (now a Republican presidential candidate), had returned to Vietnam with a delegation of official guests for the Republic of Vietnam's National Day--its last, though we didn't know that then. We did know that Saigon's army was tired and that the power of the South Vietnamese government and its leader, Nguyen Van Thieu, seemed to be waning. For the first time in years, large anti-government demonstrations were occurring on the streets of Saigon, in protest of corruption in Thieu's regime. In response, Thieu dismissed several cabinet members and three of his four top military commanders--unprecedented concessions, taken by many as a sign of grave weakness.

The protests were at their height when the delegation, which included several former POWs as well as representatives of the major U.S. veterans organizations, arrived in the city. As far as I know, McCain, then still on active duty as a Navy commander, was the only one interested enough and skeptical enough to look for information beyond the sugarcoated version that was standard fare in U.S. embassy and Vietnamese government briefings.

His search led him to some of the American reporters in Saigon, of whom I was one. Several times during his visit, McCain dropped by my room, usually at night, after the group's last scheduled event. He would tell me something of what he had done and seen that day, but he seemed more interested in hearing whatever I could tell him about the situation in Vietnam.

That can be a flattering but ethically ticklish role for a reporter. Since I didn't plan to write about McCain's group--the anti-corruption movement was the big story at the time--I thought it was okay to talk with him as long as I stuck to explaining facts, without expressing opinions or trying to argue one policy position or another. The more I talked with McCain, the more impressed and interested I was. I was in some awe already, knowing about his heroism in prison. But more than his war record, what captured my sympathy and admiration was his impulse to try to learn about and understand the place and the events that had cost him five and a half years in brutal captivity.

Twenty-five years later, it's easier to recapture the quality of those talks than their substance. I don't remember any discussion of the big questions or the rights and wrongs of U.S. policy. McCain wanted to hear about the political crisis in the streets of Saigon and how the war was going on Vietnam's nameless, numberless battlefields.

Unlike many of his military colleagues, he did not bristle defensively at anything that sounded critical of the South Vietnamese, or that suggested the war might not be going as well as U.S. officials were proclaiming. He listened calmly; once in a while I thought I detected a small wince, though I couldn't be sure.

Until he was shot down, McCain told me, he really hadn't known much about Vietnam. As a professional aviator, he had focused on flying his missions, not on the larger issues. But after his captivity, he had read extensively--wanting to understand what the war was about and what his ordeal had been for. He couldn't be objective about the war, he added, with that honesty that nowadays seems to so confound reporters and others in Washington's political world. After all he'd been through, he wasn't ready to think it was all for nothing, or a mistake.

Still, he had read all those books, and here he was, in a reporter's hotel room in Saigon, asking questions that he must have known might bring uncomfortable answers, certainly more uncomfortable than he and the rest of his group were likely to get from their official hosts.

I have no way to know, of course, what was going on inside McCain's head, but I had the impression of a man who was seeking answers almost against his will, driven by some inner need for truth that he might have resisted if he could.

One night, McCain knocked on my door after returning from a reception. The host, one of President Thieu's closest aides, had addressed a flowery speech to the former POWs, McCain said, declaring that no one could ever fully repay their sacrifice for the Vietnamese cause but that he and the president would do what they could. Anyone they wanted to meet, anything they wanted to see, anywhere they wanted to go, he told them, they had only to ask.

McCain stuck up his hand. He had a request, he said. He wanted to visit Con Son Island. Their host looked as if someone had come up from behind and walloped him with a two-by-four. Con Son, 50 miles off the southern coast, was the site of South Vietnam's toughest prison, where the most dangerous suspected communists and other prisoners were kept.

In 1970, Don Luce, an American antiwar activist, had led a U.S. congressional delegation to the island to publicize the brutal conditions there, including confinement of shackled prisoners in cells that became infamous as "tiger cages."

I must have looked a little stunned, too. With a tart smile, McCain explained that he had unwillingly become quite an expert on North Vietnamese prison conditions and as long as he was here, thought it would be interesting to see how our ally treated its prisoners.

I wanted to cheer out loud. Politicians, congressional aides, academics, antiwar activists, pundits and all sorts of other celebrity visitors had been trooping to Vietnam for years, and until McCain, I couldn't remember any of them looking for evidence that might challenge their views.

His hosts didn't exactly leap to respond to his request, but McCain kept pressing. A visit was finally arranged for the very last day before the group's departure. When he told me, I implored him to knock on my door when he got back, no matter how late, and tell me about it.

To the best of my recollection, McCain had never asked me not to write about our conversations. But I thought he probably felt he was talking off the record. He was at the time still a naval officer, bound by military rules and, I assumed, by a sense of obligation to national policy. McCain's struggle to get to Con Son was an article I really did want to write, but I never found the moment or the guts to pull out a notebook and say, "Wait a minute. Can I make some notes and write about this?"

It's possible that McCain would not have objected. But it certainly wouldn't have pleased his South Vietnamese hosts to have this story reported, and his own government wouldn't have been too crazy about it, either. I was too fascinated by then to risk not hearing about the trip. So I never asked, and--in what I fully recognized as a professional dereliction--silently abandoned any thought of writing about it.

As promised, McCain stopped by briefly after returning from the island. He stayed long enough to say that in his expert opinion Con Son wasn't quite as grim as the North Vietnamese camps he had been held in--but grim enough. He'd had to question camp officials fairly closely to find out how many prisoners were on the island, he said, and from the numbers he was given, it was clear to his knowledgeable eye that there was nowhere near enough space for them to have adequate outdoor exercise.

For the first time, he sounded a little guarded, though he might just have been tired and in a hurry to pack for a very early morning departure. Or, though it's only a guess, perhaps being back in a Vietnamese prison, even as a VIP visitor, was a more complicated experience than he was willing to reveal. I felt there must have been a lot more he could have said--and that I would have liked to hear.

If I didn't learn as much as I hoped about his visit to Con Son, though, I thought I had learned something valuable about John McCain and about the quality of courage: not only the physical courage he had demonstrated as a POW, but also the moral courage it took to face troubling facts instead of hiding from them.

I doubt McCain would have had any reason to think of those encounters again, but I never forgot them. They came back to mind in recent months when the issue of McCain's temper and, more generally, his emotional fitness to be president began to surface in the campaign--usually couched in the anonymous passive grammar that plagues contemporary political journalism, as in "questions have been raised about his temperament."

McCain has to prove he has the "temperament" to be president? Not to me, he doesn't. Like every other voter, I will have to decide whether he has the policy ideas I want my president to have. But when it comes to temperament, there's no doubt. If all the other candidates were as suited on that score as McCain, we would be luckier than we deserve.

Arnold Isaacs covered the Vietnam War for the Baltimore Sun and is the author of "Vietnam Shadows: The War, Its Ghosts, and Its Legacy" (Johns Hopkins University Press).