I am late weighing in on this election—late in more ways than one. Monday brought my ninety-sixth birthday, and, come November, I will be casting my nineteenth ballot in a Presidential election. My first came in 1944, when I voted for a fourth term for Franklin Delano Roosevelt, my Commander-in-Chief, with a mail-in ballot from the Central Pacific, where I was a sergeant in the Army Air Force. It was a thrilling moment for me, but not as significant as my vote on November 8th this year, the most important one of my lifetime. My country faces a danger unmatched in our history since the Cuban missile crisis, in 1962, or perhaps since 1943, when the Axis powers held most of Continental Europe, and Imperial Japan controlled the Pacific Rim, from the Aleutians to the Solomon Islands, with the outcome of that war still unknown.

The first debate impends, and the odds that Donald Trump may be elected President appear to be narrowing. I will cast my own vote for Hillary Clinton with alacrity and confidence. From the beginning, her life has been devoted to public service and to improving the lives of children and the disadvantaged. She is intelligent, strong, profoundly informed, and extraordinarily experienced in the challenges and risks of our lurching, restlessly altering world and wholly committed to the global commonality. Her well-established connections to minorities may bring some better understanding of our urban and suburban police crisis. I have wished at times that she would be less impatient or distant when questions arrive about her past actions and mistakes, but I see no evidence to support the deep-rooted suspicions that often surround her. I don’t much like the high-level moneyed introductions and contacts surrounding the Clinton Foundation, but cannot find the slightest evidence that any of this has led to something much worse—that she or anyone has illegally profited or that any legislation tilted because of it. Nothing connects or makes sense; it beats me. Ms. Clinton will make a strong and resolute President—at last, a female leader of our own—and, in the end, perhaps a unifying one.

The Trump campaign has been like no other—a tumultuous and near-irresistible reality-TV show, in which Mr. Trump plays the pouty, despicable, but riveting central character. “I can’t stand him,” people are saying, “but you know, wow, he never stops.”

We know Mr. Trump’s early transgressions by heart: the female reporter who had “blood coming out of her whatever”; the mocking of a physically impaired reporter; the maligning of a judge because of his Mexican parents; the insulting dismissal of the grieving, Gold Star-parent Khans; the promised mass deportation of eleven million—or two million—undocumented immigrants, and more. Each of these remains a disqualifier for a candidate who will represent every one of us, should he win, but we now are almost willing to turn them into colorful little impairments. “Oh, that’s ol’ Donald—that’s the way he is.”

But I stick at a different moment—the lighthearted comment he made when, in early August, an admiring veteran presented him with a replica of his Purple Heart and Mr. Trump said, “I always wanted to get the Purple Heart. This was much easier.” What? Mr. Trump is saying he wishes that he had joined the armed forces somehow (he had a chance but skimmed out, like so many others of his time) and then had died or been scarred or maimed in combat? This is the dream of a nine-year-old boy, and it impugns the five hundred thousand young Americans who have died in combat in my lifetime, and the many hundreds of thousands more whose lives were altered or shattered by their wounds of war.

I take this personally, representing as I do the last sliver of the sixteen million Americans who served in the military in my war. I had an easy time of it, and was never in combat, but, even so, as I have written, I experienced the loss of more than twenty close friends, classmates, and companions of my youth, who remain young and fresh in memory. I have named them in previous pieces, along with some wounded survivors, like my friend Gardner, an infantry captain who landed at Normandy Beach and fought at Hürtgen Forest and Aachen and the Battle of the Bulge, was twice wounded, had five Campaign stars, and received numerous decorations, including the French Croix de Guerre, but who for the rest of his life would fall into wary silence whenever a thunderstorm announced itself. Also my late brother-in-law Neil, who lay wounded on the field for two days during the battle of Belfort Gap, and who hobbled with a cane all his life, and with two canes near the end. Every American of my generation can supply stories like these, and once learned and tried to forget that, worldwide, seventy million people died in our war.

Mr. Trump was born in 1946, just after this cataclysmic event of our century, and came of age in the nineteen-sixties, when the implications and harshness of war were being debated as never before, but little or none of this seems to have penetrated for him—a candidate who wants to give nuclear arms to Japan and South Korea and wishes to remain unclear about his own inclinations as commander of our nuclear triad. This makes me deeply doubt his avowed concern for our veterans or that he has any sense of their sufferings.

Reservations like this are predictable coming from someone my age, but I will persist, hoping to catch the attention of a few much younger voters, and of those who have not yet made up their minds about this election. I do so by inviting them to share an everyday experience—the middle-of-the-night or caught-in-traffic moment when we find our hovering second thoughts still at hand and waiting: Why did I ever?... What if?... Now I can see… and come to that pause, the unwelcome reconsideration that quiets us and makes us mature. It’s the same thought that Judge Learned Hand wanted posted in every school and church and courthouse in the land: “I beseech ye … think that we may be mistaken.”

Mr. Trump has other drawbacks I haven’t mentioned: his weird fondness for Vladimir Putin; his destruction of the lives and hopes of small investors and contractors unlucky enough to have been involved in his business dealings; his bonkers five-year “birther” campaign, now withdrawn, though without accountability—but never mind all this, for now.

Mr. Trump is endlessly on record as someone who will not back down, who cannot appear to pause or lose. He is a man who must win, stay on the attack, and who thinks, first and last, “How will I look?” This is central, and what comes after it, for me, at times, is concern for what it must be like for anyone who, facing an imperative as dark and unforgiving as this, finds only the narcissist’s mirror for reassurance.

If Donald Trump wins this election, his nights in the White House will very soon resemble those of President Obama. After he bids an early goodnight to his family, he sits alone while he receives and tries to take in floods of information from almost innumerable national and international sources, much of it classified or top secret. His surroundings are stately, but the room is shadowed and silent. There are bits of promising news here and there, but always more bloodshed, sudden alarms, and unexpected lurking dangers. The import of the news is often veiled or contradictory, or simply impenetrable. The night wears on, and may contain brief hours of sleep. There’s time to tweet. A new day is arriving, and with it the latest rush of bad news—another police shooting out West, another suicide bomber in Yemen, and other urgent briefings from a world already caught up in the morning’s difficult events. He needs to respond, but the beginning of this President’s response is always reliably at hand: How will I look?