I saw Franklin D. Roosevelt only once, but the memory remains as indelible as it continues to be disturbing.

That was in October 1944, toward the end of the presidential campaign. FDR made a swing through New York City where, against the advice of his doctors and aides, he campaigned for hours from an open convertible during a cold, driving rain. I have no idea how it was that I was among the crowds lining Queens Boulevard -- was it a Saturday and thus no school, or did PS 101 in Forest Hills dismiss classes so grammar school students could see their president? -- but I shall never forget what I saw when the presidential car passed slowly by, a few feet from my curbside place.

There, in silhouette, etched against the glowering skies, was the president, rain-drenched campaign fedora, naval cape and all. To my childish eyes, his head looked massive. But that isn't what sticks in the mind. He was gray, gaunt and ghastly.

Roosevelt had exposed himself to that foul weather to dispel an issue about him then being openly discussed and privately whispered across the country. Disclaimers to the contrary, he was, in fact, dying. In six months he was dead.

I dredge up these old memories not to draw an analogy between Roosevelt in 1944 and Ronald Reagan 40 years later. None exists. The issue then was the state of the president's health. Even a child could see that something was terribly wrong. That's not the case with Reagan, despite what seems a ghoulish collective effort to insinuate it's so.

To this observer, wandering the country far away from Washington during the closing weeks of the campaign, there has been something obscene and outrageous in the sudden din about "the age factor" sounding forth over the nation's airwaves. I wouldn't be surprised to turn on the television in some motel and find reporters shouting questions at Reagan: "Just when did you start feeling ga-ga, Mr. President?" or "What's it like when you lose your marbles?"

In fact, there's simply no credible evidence that Reagan is anything other than what he has seemed: a 73-year-old man in unusually good health, with a strong constitution that enabled him to bounce back remarkably from a gunshot wound in the chest that medically could well have disabled a younger person. Nor is there anything to suggest that suddenly he's gone senile.

What's worse, all this snarling of the pack and circling of the sharks detracts from the real significance of last Sunday's extraordinary political event, one that seems certain to affect not only Reagan's reelection prospects but also to hold potentially heavy consequences for his success in a possible second term.

I offer the testimony of Rockford, Ill., Reagan country if any exists. It's the territory in which he grew up, which overwhelmingly has supported him in the past and continues to do so today.

In the past few days, I have talked with scores of people here, including a wide cross-section of Republicans, both rank and file and party leaders. Not a single person -- not one! -- thought Reagan had done well in last Sunday's debate. They all believed Mondale had done better. They were, depending on the person, "disappointed" or "depressed" or "saddened" or "troubled" by what they had seen on television.

My point is that an absolute unanimity of opinion exists about what happened. And in my experience, such political unanimity is without precedent.

In all the other comparable political encounters, beginning with Nixon-Kennedy in 1960 and on through Ford-Carter in 1976 and Carter-Reagan in 1980, no matter what the polls and pundits proclaimed over who "won" the debate -- a stupid exercise at best -- I always found many people who believed their guy had done best. That isn't the case this time.

That doesn't mean Reagan is headed for defeat. It does mean doubts about his capacity, his knowledge, his ability to handle adversity, have fully surfaced among the public. They've been there all along, but for the most part have been suppressed.

This has two consequences. Among Reagan supporters who will not defect this fall, it raises serious questions about how well he will handle the presidency in four more years.

"I had expected that Ronald Reagan would destroy Walter Mondale," one such person here said, "that the Reagan that took Carter apart in the debates, well, what chance would Mondale have against him? When it didn't happen I may have overreacted about what a great job Mondale did. The humor that Reagan had used so well in the years of campaigning wasn't there. It looked like he was having trouble remembering what the script was. Maybe he tried to remember too much. I thought he did a terrible job, and to a certain degree because I was so sure he would do so well. If that feeling is anywhere near widespread, it impacts a lot on the leadership factor for the future."

From the Democratic standpoint, there's a more immediate -- and tantalizing -- potential.

"I'm not a real wild Mondale supporter here in the city or in anything else," said Mayor John McNamara, a Democrat who works closely with business to revitalize this industrial city.

"Whether it's because he's been campaigning for four years, or not, he seems stale and shrill. What really impressed me about the debate was Mondale. I wasn't prepared for it. He was in charge right away, got better as the debate went on, and his confidence level was building at every step of the way. I think his not being shrill was incredibly effective. It was so unlike what the people of the country have seen of Mondale, and he showed a great sense of humor. When he ran over his time, he was natural, disarming. 'Okay, I'll get you next time.' I have to tell you, my overriding impression is not that it was so negative for Reagan but that it was positive for Mondale.

"You will see a renewed spirit with his team, because his team that I have seen in Rockford over the last 60 days has been demoralized, has been almost beaten down by the polls. I won't say you saw a defeatist attitude, but I'll say you saw a real questioning attitude. If anything, this will give his people on the streets that are hitting the bricks an incredible spark. Incredible spark.

"Candidly, two or three weeks ago I didn't think the guy had a prayer. But I've been thinking back to Illinois and the Thompson-Stevenson 1982 gubernatorial race, about the legitimacy of the polls and so forth. There you had again a good person but a lackluster candidate in Adlai Stevenson coming within 5,000 votes against one of the best campaigners you'd ever want to see in this state. You know, Jim Thompson can go in the board room and drink beer in the park. So it makes you question the polls. I think it's not too late at all. Just for myself, he's got me excited. I can't get over about how much stronger I feel about Mondale's performance as opposed to my reactions about Reagan's, which I felt I had seen some evidence of before. Something happened."

What happened had nothing to do with age or health. It had to do with capacity. Ronald Reagan can't afford to let it happen again.