It's a good thing John Edwards was out of the race before the Pennsylvania primary. He'd garnered a lot of labor endorsements, the United Steelworkers of America's among them, so a number of folks around here would have voted for him. And then they wouldn't just be disappointed today, they'd be angry as hell.

People's marriages are their own business. If Mr. Edwards in 2006 had an extramarital affair, or worse, with a younger woman who made videos for his campaign and if his wife forgave him, that's for their family to deal with. But what in blazes was the man doing running for president with this time bomb in his hip pocket? And what was Elizabeth Edwards thinking when she encouraged him, made speeches for him, touted the strength of their marriage in the face of adversity as an indicator of his fitness for office, knowing that he'd cheated on her?

It may seem mean-spirited to pose that question about a wronged woman fighting cancer, especially one who was so brave and determined on the campaign trail. But as a fellow survivor, I claim a little leeway.

The disease may give you a pass in some areas. Chemo-brain is a legitimate excuse for forgetting things and making mistakes. Thoughts of your own mortality may cloud your judgment and crowd out other concerns. They also might make you desperate to achieve a long-held dream while there's still time.

This last point may explain how Mrs. Edwards could have gone out on the campaign trail on her husband's behalf, knowing what she knew, exhorting voters to believe in him as she believed in him. But even in separating his infidelity from his fitness for office -- and she's certainly not the first wife to have done that, as Hillary Clinton can attest -- she must have known they were playing with fire.

The shrinks can sort out which psychological phenomena played a role in the Edwards' drama -- hubris, narcissism, co-dependency, denial. The rest of us are left to wonder how, in this post-privacy era, they imagined the secret was theirs to keep.

Somehow, it never seems to have occurred to either husband or wife that if he won the nomination and the truth emerged, as it was bound to do, about the affair with Rielle Hunter, it would take him out of the race as surely as an assassin's bullet. And that would give the Republicans four more years in the White House, at a time when voters hold them in the lowest possible esteem.

Howard Wolfson, Hillary Clinton's top adviser, may have been right when he said that Mr. Edwards had cost Mrs. Clinton the nomination. But beyond that, his ill-considered run could have set the Democratic Party back countless years. This, to paraphrase Don Corleone, voters do not forgive.

Seeking or granting private absolution is one thing. Courting public suicide while chasing the party standard is quite another. It's a rare politician who can overcome this kind of scandal, and John Edwards is no Bill Clinton. Has the name Gary Hart lost its cautionary power?

There's only one good thing to say about the Edwards fiasco. At least he didn't drag his wife out in front of the cameras for his weirdly dissociative act of semi-contrition on ABC's "Nightline."

Maybe we are finally to the point where disgraced politicians understand that cheating alone means confessing alone. On the other hand, it may have been a case of nothing-to-gain. Mr. Edwards holds no public office now and isn't running for one, so he had no need to salvage his political skin. Plus, he didn't stand to win much sympathy by putting his cancer-stricken wife on view.

One of the maddening things here is demonstrated by the eight-year terms of Bill Clinton and George W. Bush: A lying hound dog can still be an effective and popular president, while a faithful husband can be an utter disaster.

But even though the quality of one's marriage is not a good indicator of presidential timber (FDR and Ike had mistresses while Nixon, as far as we know, lived like a monk), we still insist that our candidates flaunt their family values at every opportunity. The further they go out on that limb, the harder they crash when it gives way and the more we blame them for it. This might be a fine premise for a reality game show, but it's no way to elect a leader.

Still, candidates go into the race knowing the rules. If they want to obscure their true intentions for running the country -- if, say, they're looking for an excuse to invade Iraq -- they may get away with it. But if there's a sex skeleton in the closet, it's almost certain to be exhumed. Mr. Edwards' political future can't be any more over than it already is, no matter what else comes out about his liaison with Ms. Hunter.

As for Mrs. Edwards, it may be some time before she's able to resume her role as an advocate for breast cancer research and support. Any public appearance would invite uncomfortable questions, the last thing she needs right now. That may be a bigger loss to the country than her husband's flame-out.

So what have we learned? Men shouldn't have illicit sex when preparing a presidential run. If they do, and their wives find out, the women should either dissuade them from running or refrain from misrepresenting them to the American people.

Early in the primary, when the couple announced that Mrs. Edwards' cancer had returned, some in the media pressed hard on how they could forge ahead with such an all-consuming undertaking. Turns out it was the right question, but based on the wrong premise.

This isn't the first time the media missed an essential part of the story, and it won't be the last time a politician self-destructs this way. More's the pity on both counts.