Pretty much by definition, a man who can be described as a cad is not a wholly admirable human being. There are, however, cads whose behavior shows a certain panache, an undeniable flair, a sense of humor and a genuine, if deeply flawed, humanity. Former Washington, D.C., Mayor Marion Barry, I would argue, is one of these "lovable rogue" cads.

John Edwards is not. His caddishness, it appears, has no redeeming social or political value. He's just a bad cad.

According to widely published reports, a former close Edwards aide has shopped a book proposal in which he claims that the former presidential candidate is indeed the father of his mistress's 19-month-old daughter – which Edwards has categorically denied. The aide, Andrew Young, is in a position to know: When the affair was revealed, Young allowed himself to be named as the child's father.

That was a lie, Young now says, intended to salvage what was left of Edwards' political career.

But that's not the worst of it – and certainly not the tackiest.

Young further claims that Edwards promised the mistress, Rielle Hunter, that he would marry her after his wife, Elizabeth, had died of her inoperable cancer. And that they would have a rooftop ceremony in New York. And that there would be music by the Dave Matthews Band.

That may be the most caddish thing I've ever heard.

I used to like Edwards a lot. No, I wasn't dazzled by the perfect smile or the perfect $400 haircuts or the perfect unctuousness with which he looked you in the eye and projected a top-dollar trial lawyer's showy sincerity. Whenever I had a conversation with him, I felt as if I were in a jury box listening to a well-rehearsed closing argument.

I liked the fact that all his artifice and ambition were right there on the surface. I liked his combativeness, his skill as a debater, his quick intelligence. I liked his personal saga – his up-from-the-mills rise to the top. I liked his family, and I especially liked the story of his family – the long marriage that had survived so many cruel tests. At a lunch we had in 2006, I asked about Elizabeth, whose cancer was in remission. For a moment, the persona vanished and the person appeared. There was hope in his eyes, and love, when he told me she was still disease-free.

I thought the world of Elizabeth – her toughness, her commitment, her grace – and I guess I assumed that if she loved the guy, he couldn't be all bad. I forgot the first rule of journalism: Never assume.

So when reporters from the National Enquirer cornered Edwards at the Beverly Hilton, where he had arranged a secret meeting with Hunter and the baby, I was stunned. I knew that married men sometimes stray, especially married men who are rich, famous and male-model handsome. I also knew that cancer can be brutal on marriages, and that sometimes even the strongest don't survive.

But Edwards hadn't just betrayed his wife, he had betrayed the staffers, volunteers and voters who gave him their toil and trust. He had betrayed the Democratic Party and, potentially, the nation. What if this walking scandal had somehow won the nomination? After all, Edwards knew the Enquirer was on his tail – the tabloid had done previous stories about the affair. Going to that meeting with mistress and "love child" in Beverly Hills showed a recklessness that was nothing short of pathological.

More pathology ensued. Edwards insisted it was a physical impossibility that he was the father of Hunter's daughter, as if the truth would never come out.

In the course of what Young describes as an elaborate subterfuge to conceal Edwards' paternity, two of the former senator's wealthy campaign donors were tapped for funds that went to Hunter as what would appear to be hush money. Edwards is being investigated by federal prosecutors for possible campaign-finance violations, though I think it will be hard for the law to lay a glove on him.

But looking forward, with his mistress, to the day when Elizabeth would die? Planning a post-funeral wedding? Choosing the rock band? Even if all this was just a fairy tale meant to reassure Hunter and keep her quiet, I can't have any "like" for John Edwards anymore.

The forgivable kind of cad could never do such a thing. Only the worst kind would.

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